If you instruct a sol to sort out the finances then the first thing they will get you both to do is to complete a Form E. This is full financial disclosure from both sides and you both need to detail every penny you anticipate spending - even down to things like haircuts and food for Christmas! It’s a pain to fill in but gives a great picture of your incomings/outgoings. I suspect in a lot of cases finances can be decided from this alone.
It also doesn’t necessarily have to go to court. Mediation is a much better (and far, far cheaper) way to go about deciding settlements but it does rely on both sides aiming to be reasonable. My ex refused to attend mediation.
My divorce took well over 18 months to complete, but a lot of that was complicated by my ex having his own business and he ended up being ordered to get it valued. We went to court 3 times but luckily avoided a final hearing which is where the big costs would’ve been incurred. Whole thing still cost me £46k though but I took out a litigation loan which didn’t need paying back until I’d received my settlement. I had no other way of funding the sol fees unfortunately but I still ended up with nigh on double my ex’s best offer before we went to court.
With regards to remaining living together whilst waiting for the house to sell, I do know of people that have had to do this. It’s not easy, I know I couldn’t have done it, but it’s doable. What effect it has on the children though I wouldn’t like to say. You will likely be entitled to remain in the house until your youngest leaves education but this will depend on whether or not you can afford the mortgage alone (if there is one). Or, you can get what is known as a Mesher order where the split of the equity is decided as a percentage now but doesn’t actually get shared out until the house is sold in X amount of years.
Try not to let concerns for how your ex will be able to afford to live somewhere if you get a larger share cloud your judgement here, remember that he has been the main earner in your marriage and will likely to continue to be. He’s not going to come out of this without a penny to his name - no judge would sign off a consent order that was grossly unfair to either party - and he will be ok once he’s had a chance to rebuild. My ex told unbelievable amounts of sob stories during our divorce but luckily no one really believed him as the high life he is living now firmly disproves all of them!
My ex was more than happy to leave me after I discovered his affair and had a figure for settlement in his head from day one. I am certain had someone advised him how ludicrous that amount was, he’s have begged me to let him stay. Beware this is what your husband may well be doing now, he’s scared of losing out financially and would rather stay (and cheat again) that take the risk.