I remembered that before I updated to 1.3.3 I also updated Nvidia drivers, so I decided to roll back to 314.22.
None of suggested above worked until I installed 314.22 Nvidia drivers (previously had 320-something and later 326.19 beta as Townciv suggested;) once I did that, I managed to launch latest 1.3.3 nightly on standard. Screen still flashes but only 1-2 times then game launches; normal FPS in game again.
This is really weird if you ask me. This seems to be a MTA problem since GTASA SP works well regardless of driver version. Something should be done because not everyone is willing to go through all this. MTA could lose players...
But thanks for your help, people.
Well, yeah, it's kind of obvious that HD3K is worse than 540M, lol.