Thank for the feedback Aloyse . . . it looks like all my balancing efforts paid off. Balancing is the most time consuming part of my mod, and the part that I generally receive the most criticism for, since it always involves compromises between realism and fun.
Norbingel, my Weapon Ability Quest script using the FOSE command: if Player.GetWeaponAnimType == 6 (6:TwoHandAutomatic weapon type). And the sniper rifle was labeled by Bethesda, under TYPE as a TwoHandAutomatic weapon, even though it is listed under model as "2HandRifle." So it is unfortunately going to require the same skill requirements and any other weapon of this type. I would change its type if I wasn't concerned that would make my mod incompatible with any other mod that makes any changes to sniper rifles. I should perhaps change the message to be less specific, even though it is technically correct in how Bethesda defined the sniper rifle.
I have no idea why your message flashed for 5 minutes . . . I just tested this in my own game, and the message displayed perfectly . . . it popped up when I tried to use the sniper rifle, lasted about 5 seconds (I didn't actually time it), then it disappeared. It didn't flash at all.
I don't know how to add an up-hill penalty, other than running, jumping, sneaking, and swimming, the only other movement references I can find in the GECK are not moving, forward, backward, left, right . . . and a few for turning states. I know of no way to tell if an actor is going up hill. I could add a sit bonus, but I just felt that would fall under is not moving, since that is a pretty generous Strain decreasing rate (it takes less than 5 game minutes to fully recover after running for 24 game minutes). Plus the only time that Strain really becomes a major issue is during combat, and that would not be the best time to be sitting in a chair.