Does anyone know where's the part of the game that controls the damage fx?

[665c3519e63e0denialol]

The strobe whenever the player gets hurt is annoying, especially when being shot multiple times. Where is the place where it is stored?

[665c3519e6669Join2]

That "annoying strobe" lets you know you're being attacked, the only consistent feedback. Without it, there's only pain sounds (which is partially random in most games), HP bar depletion which is easy to miss since it's a small bar in the corner of the screen that doesn't animate/flash when taking damage, and blood effects which is only seen when attacked from the front.
The flash also abstracts suffering pain well enough. Getting hurt IS annoying, and suffering blows to the head and whatnot does result in vision flashes.

I can't answer your question but I'd advise against removing it. Tone it down perhaps, but don't remove it.