the armor could be special in some way...it definately not something you can pick up at the local armor shop id imagine. It seems to be made specifically for him, and for the purpose of fighting yoma. The sword as well, like David mentioned, is slightly different from a claymore. its big, but not quite as big (seems that way to me atleast), and is probably lighter then a normal claymore.

As for the little girl being a demon spawn theory, i like it, but we've never seen anything to suggest mating is possible for AB's. Though since they' used to be human, i guess we can't count it out either.