I think the drop in battles are suffering from similar bugs to the rest of MP by the sounds of it, hopefully be fixed whenever they get a patch out.

As for clans theres a huge list over at totalwar.com, not sure if theres one here also also one of the mods can correct me if there is.
Joining a good clan will help your improve you ratio with training and tips, also Kocmoc has written a decent guide in the stickys here.
Glad you enjoy MP, this is the best MP since Shogun and MTW 1 imo.