Disclaimer: Your attorney will know best for your state, and I am only speaking about my experience in my state with regard to equitable distribution.
Equitable distribution means fair, not necessarily equal, and anything (both assets and debts) acquired during the marriage is included (some inheritances can be excluded). Because of this, since you refinanced the first student loan with the HELOC during the marriage, you are likely on the hook. Same for the second student loan since it was acquired during the marriage, whether you signed the document or not. He could argue that his education gained from that loan benefited the marriage. Obviously, there are a lot of possible facets to such an argument. I'm speaking in general terms. And, of course, arguing in court or through attorneys can get very expensive.
That new car sitting in the garage? You are entitled to half the value as a marital asset (look up NADA/Kelly Blue Book value), as well as any other vehicles.
You can also demand an accounting of the money taken out of the 401k, but if it was spent in cash, he will probably lie and it will be difficult to prove anything.
My state allows for recouping assets that were dissipated. For example, if money was squandered on entertaining/supporting his side pieces I would have been entitled to half as it was marital money spent.
So, with all that, you have to determine a game plan of what you *really* want out of the settlement. Then negotiate accordingly to try to get it. What do I mean by that?
I'll use my case. Xhole dissipated easily in excess of $50,000 on one of his OW alone over a 15 year period. And I could prove it. I kept that info in my back pocket for the time being.
What I really wanted was the marital home and all equity (he squandered all liquid assets). But I also knew he wanted all the recreational toys and his firearm collection. Those toys and that collection was worth a good chunk of change. All assets need to have a value placed on them - market value. I went through the effort of valuing everything, documenting my claim as to their values (so he wouldn't come back and say it was just my opinion, which is all he had).
You list all assets (with their values) and all debts acquired during the marriage and split them up (by value). In our case, the judge looks for "fair," not necessarily equal. But there needs to be something compelling to justify anything less than somewhat equal. That's when dissipation of assets comes in.
I *could* have claimed more of the assets due to the documented dissipation. However, he would have fought that and it would have required a contested divorce, meaning much more legal cost as opposed to a cheap dissolution (uncontested divorce).
So I came up with a list of everything divided up. To make it somewhat equal to appease Xhole, I took on a little more of the debt. He got all the toys and firearms that he really wanted. The bottom line net (assets + debts) for both of us was pretty close to being equal.
The reason I took on a little more debt is because my name was tied to it, and I did not trust him to pay it off and not flush my credit any further down the toilet than he had already done. In hindsight, it was the best decision I made because he ended up with default judgments against him down the road for failure to pay debts.
Back to the dissipation of assets. When Xhole started to balk a little I told him if he didn't want to agree, we would go through a contested divorce and I would drag him and his OW through the mud in public for all to see. I would also fight for my half of all dissipated assets and he would be paying me likely for the rest of his life, with his image publicly torn to shreds (his image as a good guy means everything to him).
He then decided my initial offer was fair and signed the papers. The judge asked during the hearing why I was getting the house and all equity, but once he saw that Xhole was getting other assets in exchange (as well as less than half the debt) and the net values were close to equal he didn't bat an eye. That meant a successful, cheap, and very fast uncontested divorce.
I also knew that I would be fighting him endlessly for payment of those dissipated assets for years because of his financial ineptitude and it was worth it NOT to actually go after them. Just having the info as legal ammunition for a viable threat was what helped.
I explained all that to show that equitable distribution is all about negotiation and strategy. You generally ask for more initially knowing you can relinquish some things during the negotiation that you never cared about anyway.
If your state has alimony/spousal support, you can also look into that since he makes much more than you. In my state it is really not an option except under extreme cases.
If you want less of the debt, that generally means he will get more assets to offset it (to compensate for him taking more debt). Think of ALL assets and put values on them - house, cars, furniture, collections, expensive toys, etc. It all adds up. Think Craigslist/garage sale values (market values).
Have your attorney push for the financial disclosures from him. Anything earned in the 401k during the marriage is a marital asset (the same goes for any retirement you may have), and it gets included in the negotiations, regardless of what he spent it on.
To reiterate, all this is what my experience was with regard to equitable distribution in my state. Your state laws may be entirely different and you need to talk to your attorney and/or do some homework online to see how it plays out in your state. And, of course, the issue of child support is separate and generally driven by a standard formula in your state that you can usually look up online.
Lastly, not to sound like a real downer, the judge won't give a rip where your STBX lives after he moves out and whether he pays for rent or not. And your STBX may be of the opinion that your child can make new friends in a different school if you can't afford to stay where you currently live. Regardless of how cold he may be about it, it likely won't play into the legal part of an equitable distribution negotiation (but discuss with your attorney).
I'm sorry you are going through this. It truly sucks.