Oh mieow your postings make me so sad.
I only know you from reading your comments on other threads, but I do tend to pick up on yours, probably because we both have children with cp.
Please feel free to totally ignore anything I have to say, but this is how I see your situation.
You are 24 and have 3 (?) children, the first 2 having cp. Having one child with a disability is hard enough, but 2 must be very stressful, and you had them when still young (compared to me). There are bound to be times when you wonder where your life went, and sometimes this is all you can think about. It's a round of physio, appointments, physical exertion, major planning, and there just never seems to be any fun, just one long round of drudgery. You want to discover new and exciting things to do depsite the love you have for your children, because that is not enough to keep you going, you need more.
Things are going downhill with you and dh at the moment which makes you think of other pastures even more , and then you bump into this guy. All the feelings you used to have for him have come back and suddenly you feel like you used to and you like it. So it is making you question everything about your life and if you are really happy.
The problem is that these feelings for the other man are based on how you felt for him all those years ago, when things were possibly less difficult, and there was more to look forward to.
I don't want to be brutal with you, but have you stopped to think if this guy would consider having a relationship with you in the situation you are now? You and dh love your children there is no question of that, but how would you feel if this new man rejected them? It's hard enough to cope with our own children with a disabliity, could he cope with someone elses? There's not a lot of excitement in childcare at the best of times. Would these feelings you have for him still be there if you were living a real life that included him? I don't need to tell you how people react to children like ours, you have seen it first hand I know. All I am saying is that your feelings for him are not based in this life you have now, so before you do anything about it, please have a long hard think .
If you are truly unhappy with dh and nothing will fix that, then I agree that you should leave him for yourself, but don't jump from one relationship straight into to another. Take some time to decide what you need and be happy with that choice.
I know nothing has happened with this man yet, and you don't strike me as someone who would act first and think later, but I just wanted to let you know I have been thinking about you. Take care and best wishes.