Flickering in Safari after switching back to integrated graphics
1.) This is a known Apple issue. It's insane that it existed in the first place, and it's worse that it still exists, and effects every dual-GPU Mac I have seen (in the office, at home, friends' laptops, etc). So yes, LOTS of people have this problem.

2.) Use gfxCardStatus to keep it locked in discrete mode, keep restarting Safari, or switch to Chrome. The Webkit nightly build isn't fixed, so I'm not sure when a 'real' solution will come about.

3.) That's very unlikely. As I said in (1), this problem effects all sorts of Macs, most of which do not have CUDA installed at all. It also looks like a problem with the Intel GPUs, not the nVidia ones.

Sorry for the bad news!