I'm sorry I've found this post so late. How are you now? Did these answers help? I agree with all of them, and it's heart-breaking to read of your problem.
My situation has mirrored yours in terms of 2 babies, back to work and then staying at home, and now being on the verge of being able to get a part-time job and get a bit of my life back. All the time, my husband has had his football 3 or 4 times a week, which did interfere with weekends, but which I insisted he cut down on quite early on. It was a tricky time, but we negotiated a bit and got through it as a committed couple.
However, he's always been supportive and helpful and is still in no hurry to shove me out to work again. The point I'm trying to make is that there HAS to be give and take, and you obviously do ALL the giving. Normal couples have the same problems you describe, but they should be able to discuss the tricky stuff and reach a joint decision. This is no life for you. A couple should be able to share the responsibilities of family life - you shouldn't be shouldering it all, and definitely not paying for it all aswell.
Get some legal advice. Don't, in this instance, put the children first. Putting your well-being first will be what's right for them as a knock-on effect. My sister was in your situation, exactly, and one day her daughter asked "Why do you let Dad treat you so awfully?" and that was what it took for her to realise that staying was doing more long-term harm than leaving EVER could. They are now divorced and my niece is a fantastic 16 year old who sees both parents, and who has a healthy role model - a happy mum. Don't wait for the problem to resolve itself - it'll get worse. If you separate, it'll get worse, but then it'll get better.
If you ever want to chat or email, let me know - I really feel for you xxx