So sorry to hear this
@EiffelTower and it's so easy to do and hide, with online gambling. All I can suggest is getting in touch with GA- gamblers anonymous who will have loads of experience with this. If evenings are the issue, can you arrange something else to keep your mind busy. I realise this is a simplistic suggestion but worth a try. Could you change your thinking to not wanting to make a bad situation worse (by loosing more), although again I know it's not that simple.
Id say get in touch with GA asap as the first step.
Longer term (not for today)you might explore whether it's the right thing to have a hidden savings account -this might be ok depending on your relationship but in mine I wouldn't be happy..
At the minute your kids are happy. They've got a roof over their head, a warm house, food on the table and a dad who loves them. Take steps to get help.
Realised after saying I could only suggest GA I've suggested quite a bit

. Sorry for the ramble but I hope some of it helps.