On to something more important, eh?
For my last two cents (until I think of something else) the problem is that we live in a world that's drunken with Aristotelian logic.
Secular society indoctrinates us from birth to define existence in binary terms -- if this; then that. A and B, or ~A and B, or A and ~B, or ~A and ~B.
However, the Christian world view takes in a third force -- the seemingly contradictory, yet completely sovereign and omnipotent mind of God.
It's no coincidence that the Trinity is threefold, and that the third part of the Trinity, the Holy Spirit, is the one which gives most people pause.
The very essence of Christianity is an affront to Aristotelian logic since it requires that we hold two, apparently contradictory beliefs, at the same time. And this third belief is not a synthesis of the first two. It is an entirely separate belief, i.e. "Christ is God. Christ is man. Christ is both God and man." Not a blending of the two, but an third entity.
So the basis of Christianity IS NOT LOGIC, although it is very logical, as barristers John Calvin and P-Marlowe often assert.
Thus, from before time, God knew the names of the elect, even though those names were still fallen and damned by original sin.
How can this be? Logic tells us that those factors are mutually-exclusive, that those names are either/or, damned or elect. But they are both, at the same time. As God wills.
So your search, xzins, for the logic behind Predestination is futile. Just as proving the logic of the Trinity is impossible.
"Regeneration" is a human description for the supernatural edict of God's will, known by Him from before time. There is a moment on Earth when man understands he's been regenerated (sometimes instantaneous; sometimes progressive, like Marlowe describes). But God has known it always. Any "gap" is from our perspective. The gift of eternal salvation is not just future tense salvation; it's also past tense. Our salvation will last forever and was written by God from before time -- eternal.
So all the logic in the world cannot ease your discomfort because the truth lies outside A and B. Ultimately, what gives us assurance are the questions with no logical answers except "God's ordained, holy and divine will."
Maybe as an exercise, since it runs counter to everything we're taught from day one, you could try answering all your questions and concerns with "It's God's will."
See how it goes.