1. yes
2. no
3. yes, for example if your only hero was Halbarad, then only 33% of your rangers could shoot.
Couple of things to note about GC. First, that rangers all come with bows...you pay for them in the profile and there is no way to drop the bow and gain the point. (Same goes for Riders of Rohan.) So if you're going with the 33% limit, the custom is that only those rangers posed as shooting can actually fire their bows.
Second is that GC with 100% bows is not very fun to play against, so if you're trying to have fun with others, make a point of getting into the fray rather than just advancing into range and then backing up. Your friends will appreciate it
Personally I like using GC as allies to replace the bow contingent in, say, Gondor, so it would be roughly 67% Gondor without bows, and 33% GC. Feels fair and has good flavour.
Arathorn and Halbarad are great mid-range heroes. Hope you enjoy!