OP - take a deep breath, sweetheart. You are in a difficult place, right now, and I think you have been handling it well. If there is asvice here which just isn't appropriate for you at the moment, then ignore it. You have enough going on!
I don't want to worry you further, but given that you seem to have covered all the possible routes of your H finding out about the account (mole, post etc) there is one lousy possibility left ...... you said you set up online banking, so is it possible he has set up spy softwear on your computer> its ridiculously easy to do, and you would never know it is there,. Some programmes don;t even show up in the programmes list.
Please don;t think I am saying this to worry or frighten you, but it is the only other route to his finding out about the account, that I can think of.
At the moment, I would play it cool but please just try to make sure that your mum always knows exactly what the situation is from day to day, and arrange a code call ....so she appears to just randomly call you, but is actually also checking that everything is OK.
You have been planning well, and handling things well up until now .....don't let this setback scare you too badly, just continue to ensure you stay safe.
