M - I fully believe that you have the best interest of your kids at heart. You have taken the time to sit down with your kids and actually ask them what they would like and how they feel about the situation. You have contacted a child psychologist to ensure that you are acting in the best interest of your children and to make sure that their emotional needs are met.
The thing that makes me suspicious of your H's intentions is the timing of when his demands changed. Up until the time that you filed for S, he was not requesting 50/50. Maybe your H is a changed man and really is willing to sacrifice his work and lifestyle to have the kids 50/50, but I think that he needs to show that over time.
I think that it would be really helpful if all four of you could meet with the child psychologist/counselor. If you can get a third party involved who does not have a vested interest, maybe your H will listen and come up with a realistic plan.
