Loved it! Nicely exposited, great dialog, a few fun reveals along the way. Funny last line! Although it leaves mysterious how the previous marks got there, or why Tom did wait so long to start the swap.
I'm really glad that you didn't go for a darker ending. I'm happy that they ended up together in the end. Nice to see all the guilty parties got appropriately punished as well. I'm also a bit of a sap for happy endings.