To, I don't mean to bombard you with feedback, but I really have to say that I think less is more. Your texting appears that you are trying too hard to look like you are detached, which could be perceive as just that. He knows you are hurt, so this appears unnatural. I honestly don't think you should call him or text him at all. There is no reason to make nice or appear friendly with the man that just broke your heart and walked out on your family. The "haha" and trying to connect about the kids is something that comes months or years down the line after detachment has occurred IMO.
Now I am not in your (very painful) shoes, but as an outsider there is a giant discrepancy between how you feel and your actions and I think he is bound to pick up on that. Plus, why let him think he can just walk out and you are still are going to be buddies with him? That's not a healthy response of a person with any self confidence. I am not suggesting you be rude or play games, but you do not have to pursue this type of dynamic at all. Let him do all initiating and pursing of communication, and you can step back and give him no hints of where you are at. He is not safe for you right now.
Can you go as dark as possible and take an all business approach? At least for a few months so your emotions can simmer down? I would say no calling and texting unless a medical emergency. In terms of a schedule with kids, I would email a very simple/concise, matter of fact format, schedule proposal. One that leaves little room for negotiation or ongoing discussions. You can also include that he please stick to it and that you and the kids need consistency right now. The email also keeps an organozed paper-trail. And personally, I would not allow him to come/go late at night or even spend the night on the couch, as he is not even helpful.
Sorry if this is blunt. I tend to take a very firm line approach to people like your H, and I did the same with mine. I had to teach him how to treat me. IMO, less is always more--less communication, less interactions, less seeing him at all, no pretend family time or he pretends to help, etc--just keep that in mind, when in doubt. Until he feels the consequences of his actions or the loss of you, he has no reason to want to come back.
More so, don't you deserve better than this? And don't you kids? Really think about it. Do you want to be buddies with someone that treats you like crap? He gets a friendly text from his Ex when he starts treating her and the kids with kindness and respect. That can take a long time for anyone tho.
Blu
“Forgiveness liberates the soul. It removes fear. That is why it is such a powerful weapon.” – Nelson Mandela
