I understand how you feel but unfortunately you are going to have to somehow let go of the idea that you can redress the balance through separation and divorce. Just because you've always done more doesn't mean he's going to step up now, sadly. The difference is that at least you will only be doing it all for yourself and your children, and not for him as well.
If it got to the point of going to court for a child arrangements order, they would focus on what's in the best interests of the children, so that's what you need to focus on, too. Obviously it's in their interests to live mainly with you, since you've been the primary carer. However, it is also in their interests to have contact with their father, and the details of that have to be worked out, such as enabling them to have a routine if possible (ie if he can fit work trips around fixed contact times), allowing them to continue any extra curricular activities they do, etc etc.
The finances are separate. If you haven't yet done so you should get the house valued, and review all the accounts ie how much mortgage is outstanding, any other debts, any savings in individual/joint names, value of pension pots, etc. Gather as much info as you can before consulting a solicitor. If there's enough overall for you to stay in the family home and his share to be signed over to you (in exchange for a greater share of pensions, maybe) that might happen, but he'll need to house himself and will want somewhere the children can stay overnight too. So you will have to consider his housing needs too.
How reasonable do you think he is likely to be about reaching an agreement about the children and finances? Family mediation is almost always a good idea. You have to try it before you can go to court.