it clearly says "OUR" not solely OP's. there's no point in not having accounts and whatnot linked if you're married.

as you were obviously present for the confrontation, what exactly was said? you sound very confident that that's not what was actually said. so let's hear it. also you need proof

They probably weren't or were paying absolute minimum. Since their husband was the one who ran up the charges he's probably been hiding the credit card bill and doing the "Oh I already handled it" or "I'll deal with the credit card payment" to keep his wife in the dark. Since the card is in both their names late payments would also cause issues for both of their credit scores.