Buddy reminded me that Credit Karma has a tax filing service for free. So I just went through and entered in all my applicable info, dependents, etc. -- essentially did the same thing HR Block did, and the return amount is estimated at the exact amount we had deposited.
I went by HR Block today and they said the glitch was related to child tax credit (confirming what they said on the phone).
So, at this point I think I'm out of the woods on this.
This money will go towards our mortgage payment's monthly nest egg. As of now we have 5 months of mortgage payments saved for when we move. That way, if the house doesn't sell or is delayed, we aren't tight on our budget at the new place due to paying rent/mortgage or mortgage/mortgage. If all goes quickly and well, we'll shift it to paying off any vehicle debt we may have at that time.
Once we do that, the only debt we will have is a house, when we decide to buy again.