Just had to comment on your conversation with your husband. I have a saying I go by..."First understand, then be understood". You did an awesome job of that...letting him speak and validating then moving on to validating your position. Big Kudo's...even though American hockey is better than Canadian...lol.
On the mortgage account.....since that seems to be the only bill coming out of it. You may be stuck unless your bank helps you out. I am wondering if there is way that the bank would limit withdrawals to only the mortgage company (or bank). It may not be possible, but worth a quick phone call. Just explain the situation to the banker and see what they can do for you.
Just a tough one....because there is probably no way to limit access to the account.
