Mediation can be a great choice for couples who are equals and are exiting a fairly healthy relationship and both intend to do so on good terms.
This is not you.
Your husband is abusive. He knows how to manipulate you. He knows what buttons to push. He knows what will make you anxious and afraid enough to give him what he wants so that you can just end this, which won't be good for you. You're a para - most paras I know make a little over minimum wage and have poor benefits, if any - the pay scale for paras is a disgrace given the work that you do, but that's another topic. As a software pro, he has the experience to make a lot more than you and you should be able to get a portion of his income as child support and/or spousal support until the kids are grown and you make enough to support yourself. And if there is equity in the house and it's being sold, part of that is yours - if you really are in California, that's a community property state, which means that half of any property acquired in the marriage is yours. He doesn't get to pay out the proceeds of the house in place of spousal support.
There are firm guidelines for child support and he'll have to pay that according to your state's guidelines. Have this done via wage garnishment so the money comes straight to your bank account from his paycheck without having to rely on him deciding whether or not to pay you.
He doesn't get to decide whether or not he will pay you alimony or how he will pay it. Spousal support is more flexible and varies by state so it's hard for anyone who isn't in your state to share advice or experience. In my state, judges have more discretion over spousal support so there is room for negotiation but still, there are guidelines.
If I were you, I'd forget about mediation and go with a lawyer. Your lawyer and his can work with the two of you to come to terms that you all agree with. This is different from mediation because in a mediation, the mediator works for both of you. With attorneys, your lawyer works just for you and in your best interest and will educate you on what you have a right to. So your lawyers go back and forth, and if you can come to a fair agreement, that gets presented to a judge for approval. If you can't agree, some items will need to go before the judge for him or her to decide, which will require a trial. This gets very expensive and you might not like the ruling, so it's best to get something you can agree on if that's possible. If he refuses to even reasonable terms then you might have to go to trial but hopefully his lawyer and yours can help get to a reasonable agreement.
In the meantime, document anything that you think is related to your case (threats, abusive language) and ignore the rest of what he says. He doesn't get to call the shots anymore and that will make him angry. He can say whatever he wants, but he's not the law and he doesn't get to decide.
Good luck to you, and congrats on taking steps to end this abusive marriage. That is very difficult to do. There will be hard days during the divorce process (I lost a lot of sleep during mine) but the peace you get at the end is worth it.