I have never posted on this exchange before - but I read this and couldn't help myself.

Let me first say I have no background in parenting other than raising my 2 children. I have read no parenting books nor think I am the best parent in the world.

If I was in your situation I would kick him out. Simple and plain. He is an adult and you are no longer responsive for raising him. Your job is over. When I say kick out I do not mean give him time to find a place, help him with rent, or any of that bull s***. I mean get him out that day. But it sounds like you have a history of letting him walk all over you so you probably wont do that. The reason I say "have a history of getting walked on" is because if he has the gall to speak to you like that - it didnt develop overnight. Also the fact that he speaks to you like that reflects on your parenting...You need to grow a pair and be hard on the little ******.

If he needs help then he needs to learn how to treat those who help him with respect. I bet if he treated anyone else the way he treats you - especially in their respective houses - not one person in their right mind would put up with it. It is your job as a parent to prepare him for the harsh reality of the world - and coddling him will not do that.

Don't worry about him liking you - either he will grow up or he will not. Plus he will always love you despite what you may think.

he says not to piss him off because if I do, be prepared for his rage; he will stop at nothing to bury me.

That is a threat, and you should call the police to report it.

For your son to respect you, first you have to respect yourself.

"What can i do?"

Well it depends on what responses from him you're willing to put up with. Are you willing to get in a fight over this? Are you willing to have him be mad at you? Are you willing to have him say unloving things to you and leave? It seems as though you're not:

"he moved back home (completely free)"

"respect....he says I must earn it."

"he says not to piss him off"

"in the end he will move out and all of it will be my fault"

He sounds to me like the one in charge of your house, not you. It's clear that you love him and you don't want to lose him, but he is an adult now, not a child. And your relationship with him is now between two adults, not an adult and a child. He's past the age where you can just make him do what you want.

So it sounds like it's time for you to do two hard things: treat him like an adult and act like one yourself. Your house is your house. You make the rules and you follow through with consequences if those rules aren't followed. This may sound harsh and unloving but this is exactly what your son needs. It's clear he left his previous living situation confidently knowing that your house was available. You're his safety net. He doesn't have to try very hard in life or take responsibility for his actions because he knows that mom will always bail him out.

So stop bailing him out. Lovingly tell him that he's an adult and you expect him to act like one. Adults put responsibility before privilege. Bring up the incident with the dog poop in the hallway and tell him that in the future you expect him to pick up his own mess. If he refuses, then tell him you expect him to find a new place to live within two weeks. If he refuses to budge after two weeks, tell him that you love him and will always do what's best for him, and then say that you will call the police to have him forcefully removed. You might think this is overdoing it, but it's not. It's exactly what he needs.

And after all of this he may still blame you and try to push your buttons to make you feel as bad as possible. But again, he is an adult and that is now his choice, and there are no guarantees here. Sometimes the most loving thing you can do for someone is to let them suffer a bit. If you never let him suffer he will never learn.

And he says not to piss him off because if I do, be prepared for his rage; he will stop at nothing to bury me.

This is a serious threat. And he has shown he will not shy away from physical violence:

(...) had him arrested at 16 for shoving me into the wall (...)

You are in an abusive relationship with your son. Get out.

You and your husband need to get your son out of the house and — I'm sorry to say this — preferably arrested. He has gotten physical in the past, he has threatened you now. There is no reason to believe this to be an empty threat.

You and your husband will need to plan how to maximise your safety while doing this, but this needs to be done. You may still love your son but I don't see any evidence he loves you back.

This seems to me analogous to living with an alcoholic: you go along with their behaviour, and eventually you're living in a situation with someone else's 'rules'.

"... be prepared for his rage; he will stop at nothing to bury me" sounds threatening. I'm not sure what you can do; I recommend you get some counseling (advice) from someone with experience: maybe a lawyer; police; women's shelter; maybe your doctor; people like that. He appears to be claiming that his uncontrolled rage would be your fault: that's unacceptable, IMO.

Another possibility might be (together with your son) a relationship counsellor: who (I imagine) might provide an environment (e.g. in their office) where you can explain your needs and motives, maybe define a plan or agree to some contract, without being threatened.

"He will tell lies and make it all about me" sounds to me like "guilt-tripping" and "gaslighting".

"... all of it will be my fault" is difficult to unpack in this format. Dare I say though that its being your fault might be, seen from another perspective, a good thing: in that maybe you should want to be "responsible", maybe you should do whatever the proper thing is, given the circumstance.

Also you could be advised to prepare a plan, to use in any emergency i.e. if and when you feel unsafe. You might not want to use that plan, but it's better (for everyone) than allowing or rewarding abuse. You might need to prepare a plan in advance because you can't plan well when you're being stressed. An example of a plan is to get out of the house (with or without your keys, ID, money, and phone), and go to a neighbour, friend, hotel, or shelter.

Assuming it's an unhealthy relationship, you should probably keep your other healthy relationships if you have any: work, friends, people with whom you share a hobby, family, professionals, self-help groups. It's typical that people in an abusive relationship become isolated; and it's easier to stay sane, and keep a sense of proportion, and of what's normal, and to set a good example (of having healthy relationships) if you're not isolated.

The first thing you need to do, is deal with his rage threat. You need to let him know that it is never acceptable to blow up at you and he cannot live with you if he does. If you aren't comfortable having that conversation with him, you should have him move out (a restraining order might be in order if it were really bad). I'm hoping it isn't that bad and he just uses it as a threat to get you to back down. My feeling is if it is used as a tool, he can control it. If he can't control it, you aren't in a good situation and need to have him move out. Once that is taken care of, I'd have a very serious talk with him laying out the situation. I'd say something like this...

You are living here, because I am a loving and generous mother. If you can't respect that, you can't live here. I expect you to help out and carry your weight. If I am asking you to do something, it's something you need to take care of. I shouldn't have to remind you to help out. I will always love you and help you out when I can, but will not allow you to be abusive towards me.

That's the basis, a lot more should go with it, based on your expectations. Do you mind him living with you for an undetermined time or do you expect him to be finding his own place. I wouldn't make a list of things he needs to do, based on his current actions I'd expect him to use it against you, if you want him to do something not on the list. If you want, keep a private list of things you have talked to him about. Consistency is very important, you can't let him chip away at you trying to get you to lower your expectations. I wouldn't expect things to change immediately, but I would come up with some criteria and timeline to evaluate the situation (and write it down). You may want to change it and that may be appropriate. Just make sure to hold onto all of it, as a record of how things are going. If you get to the point you feel it isn't working, you need to have him move out. I hope this helps a little.

For the short term, I'd simply put all agreements in writing, which contain three items each per agreement:

1. It is "measurable/quantitative" ... i.e. empty all the trash bins (kitchen, bathroom, & den) && not just "take out the trash"

2. A "by when" ... i.e. empty all the trash bins (kitchen, bathroom, & den) between 5PM and Midnight on each Thursday && not just "take out the trash, now"

3. A "measurable/quantitative" consequence in the failure to fulfill the commitment ... i.e. empty all the trash bins (kitchen, bathroom, & den) between 5PM and Midnight on each Thursday or you will be assessed a penalty of $25 per calendar day && not just "take out the trash, now, or else!"

In the long-term, I recommend a program called The Landmark Forum, and request he attend with you. If he decides not to initially, you can revisit the topic as you work to complete the curriculum. It's a six-month collection of 4 courses that might transform your life, and that of those around you.