I am going to make some comments and it is only based on my experience, so take it with a pinch of salt but if it helps then that's great.
Someone very wise told me on my thread 2 years ago some things that were hard to swallow. And they may help you too, as you contemplate ending it for good. You may feel you're standing at a precipice right now and that the decision is on your shoulders to end the marriage alone, as he is too weak to decide himself. My ExH told me he was relieved when I made the decision for him and submitted divorce papers 
But I spent 5 months beforehand hoping we'd work things out. The guilt I felt at the time was hard, as I longed for a stable father figure for my children, but it was equally important that the children saw their mother being treated with love and respect, both by a partner and by herself. Mumsnet helped me to realise that.
The message we send to our daughters when we sell ourselves short by accepting far far less than we should, can have a profound impact in how they see themselves as women and their expectations from relationships. That was hard to swallow at the time on my thread but so very true.
They also said to me at the time that I was doing my children no favours by perpetuating a situation in which their father figure was unrealiable and dishonest. As he was both. And I hope when they are older I will have shown them that I value myself too highly to be treated poorly. That is a far greater example to set for them.
I felt ill as I submitted the divorce papers, filled with doubt about the future and afraid but I look back now and I am so so thankful that I made that decision, with a lot of handholding from people on mumsnet at the time. And my ExH is still not doing much better two years on and in fact I think he would have been a serial adulterer if we'd continued and not only would I be unhappy still, but my children would have be stuck in an environment which wasn't healthy at all. My house is a place of peace and happiness these days and I sleep so well at night on my own. Not worrying about where he is, if he is being honest etc. But it was hard to begin with, the grief over the loss of my marriage and the stigma I perceived I had being a lone parent.
I come from a family where no one has divorced, and I felt strongly that I should try to make things work. But what I've learned over the past two years and was said on my thread at the time, is that what children really hate is tension, whether their parents are together or not. And I've noticed - as my ex and I have become better at co-parenting well together and being friendly and co-operative, and from observing the relationships of some friends - that my children are now growing up with much less tension than some of their peers, whose parents are together and arguing almost constantly, or who don't talk. My situation is healthier than some and my children are thriving and happy.
It seems like such a huge and scary thing to tell them it really is over and that you want to divorce but try not to make decisions based on fear - they are always our worst choices. When the dust has settled and you have some distance on it, you will see the relationship differently. Everything is clearer in retrospect. For when you give up the fear of losing him, you can calmly evaluate - is this what I want?
I couldn't see the wood for the tree's at the time and it hurt, I was very sad and needed counselling and anti depressants, but I came out the other side and am now dating a lovely man, a pilot no less and he is wonderful. It's still early days but there is a future out there for you too, if you're sure you want to end it and it is brighter.
Keep posting, we're all behind you, whatever you decide.