As for the wire size being #10 awg, because of the 20 amp receptacle you are using the branch circuit over current device, (the 2 pole breaker in this case), must be 20 amp. Not 15, not 30, it must be a 2 pole 20.....
I would exchange the receptacle and plug for 30A if I go that route.
Thanks again for your comments, I just wanted to understand what was going on.
Mike