The stimulus payment is actually an advance payment of a new credit that will be on the 2020 tax return. When you file next year, the credit will be recalculated. If you qualify for a larger payment than you receive now, the extra gets added to your refund, and if you qualify for less than you receive now, you don't have to pay it back.
This creates the possibility that when you file your 2020 tax return, and if you file jointly and include an innocent spouse claim, you might get part of the stimulus credit back next year. However, this is a very fluid situation and we don't really know what will happen in the future. At least your spouse's debt gets a significant payment applied to reduce it.
