Meg - I won't excuse your H for involving your kids like that but I will tell you... do NOT invalidate his feelings. Right OR Wrong... Correct... OR Not... your H is feeling unappreciated. That is what he voiced over and over again last night.
If you want to save your M you need to validate those feelings.
My H has his own tough road with his kids and mine. His relationship with all of them is ten thousand times better than it has ever been during our M, but I had to learn to validate and I had to get the kids to stop taking things for granted. My H works crazy long hours and makes lot of $ so our kids have nice things. He just wanted to feel appreciated.
From your viewpoint it looks like H is talking crazy talk. But, you need to take a step back and look at it from your H's... he is feeling unappreciated... he is feeling trapped and he doesn't have much respect for you at the moment.
"I'm sorry that you feel that we have taking you for granted. We really appreciate X, Y and Z. I didn't realize I wasn't taking the time or showing you in a way you felt it was important to me about everything you have done for me and the kids."
My M has taking a 180 and we are back on track - mostly because I stopped having the need to be RIGHT all the time. My H feels appreciated and his interactions with me and the kids are so wonderful right now.
If you no longer want your M then don't take his balonga - but if you think you do you need to start validating those feelings.
You will be surprised when you do --- validate. H will take a step back and most likely apologize to you and your kids about his behavior down the road a bit. My H did and does everyday now.
Your situation mirrors mine so closely... this is what works.