Hi Podo,
Unfortunately, trying to accurately put yourself in the mindset of readers of the time is very difficult (or impossible) and ultimately pointless - because the only safe and legitimate way to interpret Scripture is by Scripture, not by what we may think other readers were thinking. What they were thinking is largely irrelevant and by the time we get to what we think they were thinking it's utterly pointless as a guide to accurately interpreting the Bible. What the writer meant is the issue, not what any reader may have thought they meant.
I feel this is the fundamental error you are making, and it's the same error many JW's make on this issue.
When you read a Scripture you seem to be reasoning "what does this make me think, or what might it have made someone else think? Well then, that must be what God wants to convey, otherwise why would he have said something which would make me think this?"
This is literally "human reasoning".
Thus He says "Son", and you think "I know about Sons because Sons is a human concept. Human Sons are separate beings from their Fathers. Therefore the "Son" must be separate from the "Father" because thats what humans think about human "Sons' and "Fathers", and why would God have made me think that by saying "Son" if he didn't want to make me think that"? So the "Son" must be separate from the "Father". Any human reader would reason that way, so it must be what God wants us to think"
Do you see the inherent flaw in that kind of thinking? It's perhaps reasonable, in isolation, but it's not Scriptural. Actually, many interpretations can be reasonable but inaccurate. It's also arbitrarily applied (because it's human reasoning). For instance, it's apparently reasonable to think that as human sons are separate from their fathers, then the Biblical "Son" must be separate from the "Father". But this line of reason is not sound, because human sons also have penises, and so do their fathers. So according to the line of reasoning you used earlier to interpret Scripture, both the Biblical "Son" and the "Father" must also have penises.
Sounds silly right? And that's why you cut off your line of reasoning before that point. But it's the same line of reason. And you decide where to stop and start it at the points you feel it's "silly" or "reasonable". That's human reasoning. It's arbitrary. And it yields vastly different results depending on how each person is choosing to apply it based on what they think and what they feel.
But if "interpretations belong to God" and we consider the Scriptures to be God's word, then we are obliged to only interpret Scripture, by Scripture.
As for Psalms 2, I'm going to have to put the ball back in your court. Having read it and knowing basically what Trinitarians believe and what else the Bible says about the Messiah and the "Son" I don't honestly understand what problem Psalms 2 present to the Trinity doctrine, so you are going to have to point it out to me. You direct me to it as if it the problem should be obvious, but it's not. It may be obvious according to human reasoning, but according to the entire context of the Bible, the other things said about the Messiah, the other things said about the "Son", the reams of Scriptures applied exclusively to Jehovah which are then explicitly applied to The "Son" in the NT - according to all that and bearing all that in mind, there is no problem I see.
So break it down for me, if you don't mind?