Why not "Hi, I hope have a safe trip and I'm glad the car trade will work for next week! Talk later, Mel"
I kinda like this: upbeat, positive, non-threatening and with the expectation we will talk. Just make it sound like Mel. Don't mention OW it pushes him towards her. You want to vent do it but not to him. I know this sucks. Hang on you'll be fine.
He knows your on to him so play it cool. You gut wants to rip into him but it's not time for that now. Act don't react.
M22,H45,W45 S21/18D12 Retain faith that you will prevail in the end, regardless of the difficulties and at the same time confront the most brutal facts of your current reality, whatever they might be.
