IMC I don't allow graft weapon with two handed weapons, since the idea just dosn't work for me. House rule, not at all in the power description, but I just can't see that working...
But if you allow it: Yes to claws of the Vampire, Yes to Expansion (remember: the only things expansion does is give you a enlargement bonus to Str and increase your height and weight. No size change, damage adjustment et cetera).