First off, you are assuming I agree with Loving v. Virginia. I don't. I think SCOTUS exceeded its authority there, too. I think the Sovereign States should have been left to make that decision. And no, I disagree with you. The only reason States aren't sovereign (any more) is the South's loss of the Civil War, and earlier, the Anti-Federalists' loss in the creation of the American government.
And personally, although I don't presume to tell two people who can marry whom, I don't personally like interracial marriage. Miscegenation, to be quite frank, offends my sensibilities. If you want to do it, feel free, but don't ask me to fucking like it.
And yes, the National Guard can be Federalised. They can also refuse to be Federalised, by refusing to follow an order they consider to be in violation of their own State's constitution.