I will think on your question about how to phrase it if you decide to talk to H.
In some cases I think a discussion can be useful. I think about saying something to W because I feel that eventually I will reach the crest and once I have gone past it I will freewheel fast down the other side. I feel I owe it to W ...... no I don't owe it but I feel it is right for me to forewarn this eventuality.
I like the idea of checking if he sees a better way of living together. As already mentioned he may list off all your faults as he sees them. Or he could actually pinpoint something you could change. Of course such a conversation should ideally go both ways, so maybe reread the section in DR about asking for what you want.
You know you could just hit him with a quick but big truth bomb. State you can see he is not happy and you hope he can work through that BUTyou are not sure how much longer you will continue living like this. Don't elaborate unless pushed. Leave it at that and give him space.
If you want to add impact to it, leave for the weekend. Something different could help him hear you.
Just bare in mind if he is too stuck he may not be able to react yet.
Best wishes
R 25 years M 14 years S11 & S13 Working on it alone since Oct 2014 M in trouble a lot earlier (~2 years) Feb 2016. 1st R chat in a yr. Next R chat Aug'17 Still together