Was the posting to his computer to help you? Maybe you could post here instead. We would love to give you a whack a spouse hammer
But seriously? The message to your H is what?
I see you giving more weight to OW and H's situation than necessary.
If you want to talk about son and the implications of H's decisions, I think that it is a conversation you need to have face to face, with firm boundaries set for H and his visitation with son and your access to car for son's needs. What his part will be moving forward. What about a night off for you? Get out and have fun