There is really no excusing his further spending. It wasn’t even on things that are necessary to live, he bought a frivolous timekeeping device, when he Carrie’s a phone, doesn’t he?
I say only go forward with your eyes completely wide open that he is going to lie, conceal issues, spend more than you both have, remain secretive, even if you’re in a pact to save for you future.
Can you do that? I don’t think you can, and I really hope you don’t.