Your response was perfect. You are the main custodial parent in the household. You have the boys a large majority of time, as well as keep the household going.
Mlcers don't think about any of this when they walk out the door. In their minds, they think the bills and responsibilities will magically disappear or that the spouse will feel sorry enough for them when they cry the blues to tell them that they will pick up the tab. Life doesn't work that way in today's society. He's having to face the consequences of his actions. Yep, the old boy needs to pick up a second job and try to arrange his schedule so that he can see his children. It's not your fault he opted to create two separate household.
You can feel sorry for him, but do not allow that to soften your stance on support. Remain calm and collected when you are discussing finances w/him. This would be considered a business deal and should be dealt that way.
Good luck!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.