Can my marriage be saved?

A man does not leave his family to go pay off debt. That would only put the entire burden on his ex wife and children, and doesn't solve the problem. It costs even more to run 2 households, and he'll have child support, so he'll really be broke. You've already found the new girlfriend's phone number. You've already caught him in multiple lies about where he is, and what he's doing. What is trustworthy about any of that? He has a gf, is telling you that he's planning on leaving, is hiding messages, and is lying about it all. Wake up and smell the infidelity. He's halfway out the door, so start making plans for supporting yourself and your kids when he ditches you for the new girl.