So I start a game on Impossible difficulty. Then, I go and accidentally save over my other file where I almost had everything upgraded for that achievement on. /facepalm
Oh well, lol.
I'm doing a One Gun/Impossible run.
No idea. Do you need to work on your aim? I jumped right into the game on hard mode, and I'm doing pretty fine as far as ammo goes. I could use more health packs though, but I never buy any for some reason.