Hi Barbolani,
about your first problem, I havent experienced that in many many tests, with radio saves and retry aswell. It is weird, as the game doesnt use many variables at all. I assume you are playing 1.06, now, are you using any extra global addon for sounds, environment, etc that might be interfering with the saves?
The difficulty selector, when closed, will give you a hint showing the dificulty level. The ammo boxes close to your starting position have no relation with difficulty level, there are many random items in the game, including the presence of some ammo boxes, trucks, etc. So, in game A you might have or not some of these ammo boxes and trucks, and in game B dont, or viceversa.