Your feelings are perfectly understandable. You have shown amazing grace under pressure. It is not fun, but it is normal for you to have these feelings. Have you read any of the threads about LBS cycling? Missherlove has been posting about his cycling. I find it really helpful to read what others have written about this.
I too wonder if I am losing my sanity with the cycling that I have been doing. For me, physical activity really helps.
It seems as though being in contact with MIL and FIL is a mixed blessing for you and D. They have been put into a difficult position by H too.
Please adhere to the 48 hour rule. Don't allow yourself to respond to H for at least 48 hours. Take good care of yourself and do some very nice things for yourself. Get a pedicure.........or buy some special tea.........or a wonderfully indulgent dessert...........or curl up with a good book. Do whatever will make you feel good.