There's something I need to tell you and I don't want you to take it the wrong way. I want to make sure I phrase things properly, but please don't take offense if I fail; it's just a slip and I mean no harm. Please bear with me here as I look for a way to open up about something very minor and with no intention of hurting or upsetting you.
See what I did there? It was just a joke to suggest that maybe your "wordsmitting" is not really helping to smooth things out. Shorter, more direct emails are harder to interpret and easier to respond to. In fact, I don't think you're asking your XH for "help": you're just informing him of something you both have to do, as parents. So maybe a simple: "Hey, there are X hours of volunteering to do at the pool so that D8 remains in the team next year. Let's split it in half in a way that fits our schedules. I can take June and July, you can take August. Is that ok?"
I don't even know what your emails really look like (probably not like my intro!), so this is just an idea and you see if it resonates.
Another idea is that you can ignore his emotional reaction and respond with "Sorry" and move on. It's kind of how things go with STBX and it keeps the emotional involvement at a minimum. If I make a bigger deal of something, her short reaction makes me feel kind of silly (and vice versa, I'd say).
Finally, I'd suggest that we humans have a tendency to interpret other people's reaction as "offensive" when they are simply defensive. How many times have I seen shy people be perceived as aloof? So his silence might not be that he's upset, but that he's just unsure about how to deal with it, what kind of availability to offer. In any case, giving people the benefit of the doubt is most likely to benefit us.
By the way, my STBX and I have an agreement that we'll respond to emails within 72 hours. She asked and I agreed. It works well.
M39 D6 D3 (at S) S 2014-09 D 2016-09
"You can't start a fire sitting around, crying over a broken heart" - Bruce Springsteen.
It was just a joke to suggest that maybe your "wordsmitting" is not really helping to smooth things out. Shorter, more direct emails are harder to interpret and easier to respond to. In fact, I don't think you're asking your XH for "help": you're just informing him of something you both have to do, as parents. So maybe a simple: "Hey, there are X hours of volunteering to do at the pool so that D8 remains in the team next year. Let's split it in half in a way that fits our schedules. I can take June and July, you can take August. Is that ok?"
