Not to be a downer either, but in the case of divorce a "gift" is usually not something that is considered marital property and open for dividing. The change in value is something that could be divided, but since the house was a gift it's not even part yours by government standards no matter how much you love each other or expect to spend your life together.
It's in both of your best interests to leave the loan as is, there is no way I would give up a sub 3% interest rate just to get added to the loan. If you absolutely insist, just get added to the deed.