it is impossible to pass the level on my PC, after one shot the game does not respond with periodic recoveries and again and again, need a fairly powerful PC

Nah, you just have your setup wrong (like most). Playing fine on my old AMD with crappy video card. People always seek more power when things go bad, but use your head instead ;-)

For anyone else reading this: Why was doom able to run '3D' so well on a 386? And what did we add to doom later on? Sometimes you need to go back to the beginning to solve things.

In the topright corner you can see the FPS:

Again, i'm not running on fancy hardware. Just a simple dualcore AMD.