Hey lovely, I'm sorry you're in this situation but you seem to be handling it like an absolute trooper! I'm so impressed with how strong and determined you're being. 👍🏻
I recently handled my partners divorce from his narcissistic ex, which was drawn out due to her appealing the divorce, so it was very long and drawn out.
Just a few basics if you haven't seen a Solicitor yet...
The divorce, financial settlement and child arrangements are 3 separate distinct issues to deal with. It's often best to pause half way through the divorce at the point of the 'conditional order' (the previous 'decree nisi' first bit) to do the financial settlement bit (it's to do with pension sharing orders, as the red tape means it's easier to divy them up while you're still technically spouses).
Not selling a house until the children turn 18 isn't usually a thing these days. Judges understand that parents are more 50/50 with care (I expected not in your case!) and so previous "mesher orders" meant the leaving party couldn't afford their own decent living arrangements, and so these days a complete clean break of all finances is seen as best, not going a divorced couple together until the house can finally be sold. HOWEVER having a child with disabilities, depending on the severity, is often the exception to this rule. You might be able to argue to keep the house with him paying the mortgage. When you say that you could afford the mortgage on your own and give him half the equity, in that scenario he wouldn't really be able to force a sale. That would only be if you couldn't afford to give him the equity. Forcing a sale is a really difficult thing to get agreed in court.
An expected split after a marriage of your length would be 50/50 but it's based on NEED rather than fairness. You split everything 50/50 and it only really varies from that if one party needs more to get by. Or if there's an existing Deed of Trust to do with house deposits etc.
There's 2 ways of doing the finances. The short mutual consent way, were you just basically trust each other to honestly list your assets and incomes etc on a simple form, state the split of everything as it is, and how you both agree it will be after the settlement, get a Solicitor to draw it up into a court order and get a judge to rubber stamp it. You can always get mediation sessions to help you discuss it and agree.
Or you can go the hard way if you don't agree, fill out a 40+ page document (the firm itself made me cry!), submit statements, proof of everything etc. You then employ solicitors to argue it out for you, or professional mediators, or can submit it all to court for a judge to decide at a hearing. For this bit it can get that mounting legal fees wipe out so much of the assets that I'm sure I remember that you have to keep submitting running totals of your legal costs with your paperwork. It might have changed though!
I handled everything myself for OH, did all his divorce submissions and got it through without a hiccup (after the bit where the nutjob ex appealed the divorce and then didn't turn up the hearing, meaning the judge threw her appeal out and agreed the divorce there and then). I did all his finances up to the point needing the solicitor to draw up the court order. If you decide to do your own divorce application and want to message me about anything then feel free. There's a certain way you need to phrase the examples of unreasonable behaviour if you want the best chance of getting them through without question. Since COVID the online process has got MUCH easier for normal every day folk doing their own divorces.
Good luck, best wishes and stay strong!