I remember when I played FEAR a lot back in the day that I put into the cfg files some lines to boost graphics, like there exists a command for keeping bullet casings on the ground for as long as you want, but that was then, and I can't seem to find it or many others anywhere on the interwebs.
Anyone have any luck finding or remembering such config file tweaks?

don't know about config file editing, but there used to be a small mod called rmod that did basically what you are looking for. I can't find it anymore, but there are some other mods that might suit you:
http://www.moddb.com/games/fear/mods
https://www.nexusmods.com/fear?tab=popular+%28all+time%29

The mod I first mentioned, I found it again:
http://www.moddb.com/mods/fear-xp-rivarez-mod/downloads/fear-xp-rivarez-mod