Well, first of all, I'm very sorry to read your story. It's never easy to cope with a situation like that.
May I start with a few observations of a general nature.
The first is that you need a home, and so do your children. The Court will give some priority to the children's need for a home while they are still dependent. As the main carer, that will benefit you, as it often does.
The second is that your husband will have to pay child support according to the CSA formula. How much that is, depends on how
often he has staying access. But he will have to pay you something and by and large it is not negotiable.
The third is that you should review your entitlement to benefits in the light of the separation. A CAB should give you advice on this free of charge.
The fourth is that, if your husband does what you say he will do and move in with his NP, then his housing needs are met. So the Courts don't need to worry about where he is going to live. On any view of the situation he is comfortably off.
So you and your children clearly need a home. Let us look at the various possible options.
The first is that the house is sold and the proceeds divided.
The second is that you buy him out.
The third is that you and the children stay in the former
marital home until the youngest is 18 and the property is sold at that stage and the proceeds divided. This is what your solicitor is suggesting and
60% is well within the range of the possible. By the way, this is called in the trade a Mesher order after the case where it was first used.
There are other options but I regard them as unlikely.
Spousal maintenance - tricky. You will almost certainly get something. One issue is whether you can obtain employment. In principle you are expected to take some steps to support yourself but when there are young children involved, then my own view is that you would not be expected to seek work until your youngest starts secondary education.
That doesn't mean that you can't or shouldn't take work if you want to and if you can manage the childcare. All depends on your circumstances. I've seen women who went back to work after pregnancy on the earliest day they legally could. But as some posters have correctly observed, I'm a bit old school ( fuddy duddy if you like ) but your husband is living in a house with no mortgage and a new partner who could reasonably be expected to pay half the household costs. Even after child support he's going to be comfortably off and this is a factor very much in your favour.
Have you considered pensions ? I think you should. If you can get some share of his pension, you can top it up from your earnings.
The issue of a buy out = hmmmm, not sure.
But as I've said, the fact that he might have to wait a long time for his money
could mean that he could be attracted by an offer of 20% now rather than 40% in 13 years or so. Just a thought.
You need legal advice, without any doubt, but what is coming through to me is that you might be willing to take a settlement on the low side. I think your case is quite strong.
LMM