Rockbass setup

[OxJohnson]

I have asked about setup on this before but now I am armed with more information! So here goes:

I have a Rockbass Corvette Standard. There was a problem with buzzing on all strings above the 12th fret. I slowly took out relief and raised the saddles a little and finally got rid of that buzz...

But there was not enough relief and now it buzzes on the first and second frets... I put some relief back in and now the relief is at .035" - and the buzz is still on the 1st and 2nd frets, but now mainly on the A string. The neck looks straight with no bumps that I can see. The action is now pretty darn high. If I lower the saddles any the buzzing will start all over the neck.

So my questions are:
1) Any ideas of what to do now? I don't think it is just a high fret as I have now succeeded in chasing the problem up and down the neck.
2) Do Rockbasses just have high action (this seems absurdly high especially compared to my RD500)?
3) How many turns are typically in a nut before it can go no further? I am not forcing it, but it seemed like it took quite a few turns to ultimately get most of the relief out. I was getting worried that I was reaching the end of the line.
4) What is it about having a large relief that causes buzzing on the frets close to the bridge? I can see why having little relief causes buzzing close to the nut, but not really the other way around.
5) Does saddle height have any effect on buzz besides affecting the entire neck equally? Is there any scenario that lowering the saddles would actually reduce buzz anywhere on the neck?

This is perplexing me as it just seems like there is no way to get the buzz out! Right now my relief is way above spec and the A string is still being troublesome!

Thanks in advance,
Ox.