Honestly I think deep own your reluctance solo, is you want him back still. Your sentences are very open ended.."I wouldn't have him back straight away"....
It's fine to feel that way as it's ultimately your choice, but you do have to prepare yourself for the fact he won't.
He is making planS with BB, for the house etc. He won't be running back to his family for Christmas, he is busy plotting outragously with BB, for things in the new year, think O2 concert.
Even if you take legal advice and even start action that won't stop a reoncilliation if you want that, it may even spur it on.
Although you have come a long way, the situation hasn't has it? He is still with her, practical free reign over your house, coSy chats, using you even if it's just emotionally now.
Mean time nothing has been done by you to secure your and dc's financial stability. All the while he has probably been plotting behind your back with BB, on how to get the best deal for him.
He meanwhile plays you off against each other, he does not seem so bad then, and hopefully you don't think he is bad enough to screw you over, she does not think he will be sleeping wih you on home visits.....
I know it will be hard especially as he is around a lot this week, but you are leaving yourself as a sitting duck you really are.
Remember this man lied to you for months whilst sleeping with her, he walked out on you and the kids at the click of a finger, he has since slept with both of you, had you both on the go and probably been bad mouthing you both. He is spinless and getting worse, re, demands with dc's. FOCUS!