Realism mode is a difficulty that's supposed to be as difficult as possible. Just some modifications to your configs.

Browse local game files > Main > config.cfg
Change the following:

seta cg_drawCrosshair "1" > "0"
seta cg_hudCompassSize "1" > "0"
seta cg_hudAlpha "1" > "0"

Once you have done that. play the game on veteran difficulty and:

Treat your character's life as if it is your own: play things smart

Limit yourself to using one weapon: choose one weapon that you start with, and keep it with you until the end of that 'series of missions' (in pathfinder, burnville, dawnville and carride, I use the same weapon I started with in pathfinder)

The only exception for this rule is when you need to use a panzerfaust.

No quicksaving!

Lastly, and optionally, you can install reshade and tweak the settings to your liking.

If you feel brave enough to take on the challenge, go ahead. It's up to you. Have fun.