Have a look at the half-vampire, in Libris Motris (I believe) should give you an easy baseline to start from.

As for dominate at will, its a bit of an issue but if you read the spell its based on there's a duration, and also as a DM you should give a limit to how much the vampire can have dominated at any one time. Such as 3 + 1/2 HD + cha mod.