Db, It's interesting. You ask for advice, but your last sentence indicates that you know exactly what you want to do- distance. Then go for it. I believe you do know what you need to do next. Pull back for a while and see what happens. IF he really values your "friendship", he'll notice you're missing and you'll see if he sticks his neck out to find you.
Like you, I sense trouble in his relationship. Just don't burn bridges behind you and wait to see what happens. Time will tell. Be patient and fill your life with good things.
