Im not yet divorced so this is only based on my experience so far.
When say you can't afford the house do you mean the repayments or do you mean you couldn't buy him out yet?
With 2 children so young you might have a chance of being allowed to stay in the family home (if it went to court) until they are 18/21 so you wouldn't need to buy him out now. The house could then be sold and split as agreed.
Check entitledto and child maintenance calculator to see what you might get as a single parent before considering if you can afford the repayments.
If selling up means you can't buy again then you might be better staying put. You know your history and what seems fair.
If he cannot afford to buy by himself he might be happy to leave his money invested in the joint house.
I guess if your parents could buy him out that would give you a clean break.
I think i have paid £1400 for court fee and solicitor. £900 seemed pretty standard for a the solicitors fees where i live, £550 court fee. I'd have been happy if my H was the petitioner, I hate feeling and being treated as responsible for the divorce. And the idea of "Blame" is of no consequence in proceedings.
The £900 covers the divorce process in my case, but not financial advice.
If you do file on unreasonable behaviour grounds then it's IMO a good idea to avoid being antagonistic and just state as much as is needed. I think most lawyers would advise this too.
It is very unusual for things to get settled in court. The expectation is that you reach agreement and then the court effectively "rubber stamps" it. Your agreement just has to be broadly in line with what the court expects.
IME having no money is an issue unless you can easily agree a financial settlement. Mediation might be cheaper than court but still estimated at several thousand. Any financial advice from my solicitor is charged at an hourly rate (£250 an hour i think)
(My divorce has ground to a halt.)