Oh, my. That subjunctive again!
To be very clear on two points:
Subjunctive means so many different things to different writers in different contexts that its use can only confuse discussion. I will speak instead of real and unreal *conditional* uses.
There is not and never has been anything called a "future subjunctive" in English. When forms of will and shall are used in conditional or hypothetical clauses their reference is not temporal, to the future, but logical, to a consequence.
Let's take the passages as you have numbered them:
1) This is a direct quotation, so Yes, speech time is reference time. All the events in these two sentences occur in reference time; no verb refers to anything before or after it, so all three coincide. The use of what we conventionally call the "past" forms of shall and would is elicited by the fact that both cases represent the consequence clauses of unreal conditional (If..then) constructions in which Rivers regards the condition (the if clause) as highly uncertain. This is not immediately obvious, because the if piece is implied rather than stated: but the logic is as follows:
It is certain that
[If I could have the original,] ... CONDITION
[then] I should like to have it. ... CONSEQUENCE
[If I did acquire the original,] ... CONDITION
[then] would it be judicious &c? ... CONSEQUENCE
2) This is Jane narrating what she thought in the past reference time; but again all the events occur in that past time. Once more we have conditional constructions; but in this case Jane regarded the condition, Rivers' becoming the possessor of the original, as real--entirely possible. If she had then spoken her thoughts at that time she would have said:
"If he becomes the possessor of the original [then] he may do as much good with it &c"
This present-form construction is obscured because Jane what actually uses is a construction which rewrites [If + Subject + Verb-present] as [should + Subject + Verb-infinitive]. This is a fixed idiom; it does not change when the sentence is "backshifted" as indirect speech:
"Should he become the possessor of the original [then] he may do as much good with it &c" ⇨
It seemed to me that should he become the possessor of the original [then] he might do as much good with it &c
3) This is another direct quotation, with speech, reference and event times coinciding; it is cast as an "unreal conditional" using past forms; even though Jane is certain in her own mind that Rivers' acquiring the original is perfectly possible, she must respond directly to Rivers' question cast in the unreal form and acknowledge that he has a choice:
R: If I did acquire [=were to take to myself] the original, would it be judicious or wise?
J: It would be more judicious and wise if you were to take to yourself the original at once [than if you were to delay, or not to take it at all].