| | Re: I slapped him!
Well, you need to protect yourself from being with him in private. So that you will not be tempted to strike him again. It's understandable what you did, but you are right to be concerned about it as you have a lot of anger which is also understandable. But you can take care of yourself by asking to only switch the children at a neutral location. This might be at a local police station or a McDonald's that has a play area, etc. Anywhere there are guaranteed to be people and also a videocamera surveillance.
It sounds like you are capable of taking care of yourself, what with getting work and being the best mom you can. Even though you are not divorced it's likely you can apply for state/community aid for day care and other assistance. The state will figure out about the child support and even collect it for you. They are used to dealing with the situations you describe. They go by your actual household, and won't count all of the marital assets he is holding and you can't access.
Don't drive yourself crazy trying to control stuff you can't, such as if he leaves the kids with the 18 year old. Your kids will really be okay. It's not ideal of course but try to focus on things you actually can be in control over. You will go nuts trying to find out when and if the kids are with her. What you can control is if your kids come back physically harmed in some way. This is another benefit of meeting at a police station to change physical custody, you can inspect your kids and if there is an issue, such as bruises or severe rash, etc. you can file a report right away.
Some communities actually have special centers set up for parents who need to swap off their kids, but there is stress between the two of them.
Time will be your ally. If he did clean out 56K in a joint account, the bank statements will show the initial money and the transactions. Just because he took the money doesn't mean sharing it in a divorce won't catch up with him later. He will have to do financial disclosure, and there is a paper trail, if he tries to hide it he can be held up on lying in court and fraud.
Sorry this happened to you. Don't be too hard on yourself, we all make mistakes, both in marriage and in personal conduct. You now know you are capable of striking under extreme stress. Take care and change your environment so that you are free from the hassle of wondering if you will do that again.
IC might be helpful, although if you want it free/low cost there will probably be a waiting line. If you have insurance it would be easier, in most states you would probably qualify for adult Medicaid and that would be great because you could get counseling which is very helpful to learn to deal with anger and the emotions that feed it such as shame, humiliation, etc. You are a good person. Don't let you husband's actions define you. Soon you will be separate from him, and not have to live in the shadow of his behavior which was his choice, not yours.