i adore a good retro 3d style and you really nailed it!
2 simple little things, that i would add to the atmosphere:
find a style for the UI elements that fit to the retro 3d art style - especially the crosshair stands out as too detailed.
and 2nd: while I get that silence can be super scary, I think if you mix it up with some background noises, it could greatly the intensity... but that's just my 2 cents.