I'm assuming "??????" is actually cheats won legitimately, but perhaps there are some that can't just be typed in. I'm finding "POSTAL" level of difficulty a little challenging and wanted to increase the frequency of food drops or high powered weapons, but I didn't want to give up my chances of seeing all "??????" unlocked.

(I don't really care about the achievements.)

I'm pretty sure this will not work if you've cheated, I'll double check that.

The easiest way to decrease difficulty in POSTAL mode without having to resort to cheats (which would probably exclude you from unlocking any bonuses) would probably be to simply decrease the bystander population in the performance settings.

With a bystander population of 0 it is much easier, true.