I would try
nvda_drv=0 nv_disable=1
At boot time and see what that brings. Hook your monitor up to the onboard dvi, bios set to 1st gfx card = igpu or similar, and mem allocated to the gpu to 64mb
You basically wNt to bring back the machine to bare basics and see what that gives.
So you could disable sound , onboard network... Anything you don't desperately need. When you can get it working then you add or enable things.