Honestly, I'm going to 4x4 you, so don't read if you don't want to.
You're reply to H's email, more guilt, blame and shame and all about YOU. Not cool. You don't have to like that he asked, but did you notice how his email was succinct and to the point of what he is requesting, which is time with the kids? Your's is about, 'You did this to me, suffer, blah, blame, blah, shame, blah.'
You "got" to the kids before H - foul ball and really unfair. Your son is angry and you can fix that with grace and dignity and most importantly by showing your kids you will put them first no matter what, but you're not going to because you're angry at your H.
For months you've been wailing about how unfair H is to be doing this to you and the kids, and when a moment comes where you can shine and show your kids and H a graceful way of dealing with custody - you know, being able to think of what's best for the kids when unexpected things come up - you instead do exactly what you blame your H of doing. You'd rather your kids are miserable to punish your husband. Yuck. And not something I would expect from you. Wallow for and with yourself, don't bring the kids into it.
Donna, hate me, curse me, call me names, but you're just not getting it. I hope like he!! that you can get over this part quickly, but it's turning really ugly.