questions and doubts piled up upon even more questions and doubts! It's enough to drive one insane - and I know, because I have been there.
Think about this. If you had lost something precious, and were looking for it, and your house was really messy - I mean with junk lying around everywhere, on the floor, etc - then it would be hard to find that precious object. But if you cleaned up your house a bit, made some clear space in it, after a while you would have a better chance of finding that precious object.
In my experience, searching after the truth is the same. We need to make some space in the mind, to calm down it's excessive motion and noise, if we want to have a chance of finding out truths about ourselves (and the world, universe, etc).
I'm not saying your questions are all irrelevant. No, I think you ask some valid questions. It's just that, in order to actually answer any of them (the ones that actually have an answer, that is - not all of them do), you will need to slow down a bit, imho. Make some space in the mind.
Personally I find recollection of the body very helpful in this, particularly recollection of breathing.