In game it does, at least it should xD
In char planner it does 100%, you can check it by putting strength requirements to the 10 and having less strength apply buffout. My char planner although could have bugs (different from server bugs (: ) and be outdated, because I didn't have access to the actual information. I think my chance to hit formula is not 100% correct, and has fault in around 1-4 hexes depending on values. CTH on the right of the character planner will give more detailed info on chance to hit.
>How do you get .50 bmg
you can buy it from 2nd level weapon merchants (expensive) or loot it from core, mostly from skeletons (rare best loot containers). You need to buy from merchant of the faction, which has needed zones to be captured (merchant choice depends on amount and which exactly zones your faction has)
>What scope is needed for the DSR-50
you mean, for crafting? Sorry, I'm not sure. If you have a recipe, you can check in your fix boy.
>Is the scope sight range effect active as long as you're just HOLDING the sniper in primary?
yes. you can also hold just a scope in primary
>Is watchtower only active during sneak?
As far as I know, it's active always