Looks pretty good. A handy solder-er? would have the 12ga issue fixed in a few minutes.
after a closer look, i'm 95% sure it is 10AWG wire on the motor side and 2 10AWG wires together on the battery lead side.
They say a good mechanic only needs 2 tools - WD40 & Duct tape. If it moves, and its not supposed to, duct tape. If it doesn't move, and its supposed to, WD40.