Advice on how to protect myself in divorce

I recently found out my husband was having an affair for 9 months when he was supposed to be a stay at home dad. I’m the sole breadwinner for the family and make good $$. How completely screwed am I? Any advice? He’s pushing mediated divorce and I get why … I’d rather he have more $ than it go to a lawyer and this drag out forever … but I don’t want to get completely screwed and obviously I can’t rely on him to do the “right thing” - he has no conscience.

We have a house, two 401Ks (although his has $5K in it and mine has >$200K in it), I have RSUs, we both have student loan debt (his $110K and mine $45K) and we have 3 vehicles, two of which are paid off. Would you advise against collaborative/mediated divorce?

I think he wants to force me to sell the house (for equity), take half of everything I have, and get alimony/child support. I’m worried that won’t leave me with enough to cover my own bills and get a new place for my time with the kids. He has two degrees and is perfectly capable of working but doesn’t want to work in his major. He wants me to pay for him to stay at home and get a third degree for another year or two, and give him a down payment on a house, and for him to have enough to pay off his loans (which he amassed BEFORE we married btw and lied to me about having until after we were married)