When I rotate a bone on my rigged character, the character rotates 2 times as much as the bone. I can’t figure out a way to solve this, it becomes a problem when trying to animate more flexible positions
You (most probably) have wrongly assigned vertex groups and/or influence of each bone. I guess that rotation of part assigned to your Leg.B bone is not exactly twice as big as bones rotation but it just looks much bigger. This may be due to accumulated rotations of THAT bone and some other one (it parent, for example). You may wish to send the blend here for me or somebody else to fix it (if you cannot correct it yourself) 
Regards,