Hello - having just been dumped out of the divorce process I can probably advise a little.
You are assumed to have equally contributed to the marriage. A marriage is more than just the income generated otherwise it's 'just a business'. ...you know, things like housework, raising kids, having laughs, being a companion and all sorts of other things that go into making a home with someone. So a solicitor will tell you: the starting point is half of all marital assets (inc pensions) and it's adjusted for needs after that. Not who earnt what. He is assumed to have needs too.
Your children are the first priority. They need a home and at least one adult to supervise them! A parent is usually considered the best adult for this job.
So it's not about the percentage split but necessity. If there's more than enough to go around then it's 50/50 of all assets (including pensions), if not then it's about needs.
He'll have a tough time proving that you put a gun to his head and forced him to have children with you and paying into a pension or buying shares, day after day after day! But when he promised 'til death do us part I assume he did this voluntarily too. Whilst he can regret his decisions, he can't unmake them. The children ain't going back in the same way they came out...
I always recommend the book 'Family Law Made Simple' by Gordon and Slater to help you understand all the different ways of getting divorced and what the process involves. It's complicated!
Essentially, you only get what you negotiate. You are quite entitled to walk away with nothing if that's what you chose.
As for a solicitor. A 'simple' divorce costs around 5 - 10K with a solicitor's help. If you end up going all the way to a final hearing, you can multiply that x2 for every time you have to go to court, and x3 or x 4 if you use barristers too. If you use top-end solicitors, well just add lots of noughts...
However, you can just use a solicitor for advice and do all the paperwork and legwork yourself (Wikivorce is handy) to keep costs really low (e.g. less than 2K).
So if you're going the solicitor route, then it's going to have to get you more than he's prepared to give. For some of us, that's not difficult to work out. It's not about being 'grabby' its about making sure you can provide for your children and their primary carer (you!).
However, irrespective of whether or not you use solicitors, if you can't agree between you, or via a solicitor, then you have the sheer joy of mediation, which is considerably cheaper, and which can be very successful at covering all the issues that need to be thought about. It can also be a jolly expensive waste of time. Occasionally, you can get a judge to excuse you from it but that's very rare.
So ask him for full disclosure now. Then propose mediation, but yes, do get some legal advice. Even if it's from a book.