I've got major concerns for you, girlfriend. The dynamics going on in your life, in my opinion, have nothing to do with your xH and deciding whether or not this R is workable. I'm going to disagree with blackfoot here and say, whether he cares for you or not is NOT the issue.... whether he can change or is willing to change, or have sex ever again in his life is NOT the issue.
YOU are the issue... what is driving you, internally, is the issue.... and I think since you are unclear about what is 'driving' you, you are continuing to be confused by seemingly outside occurrences and using them as the reasons for the discontent in your life... reasons for the problems in your life.
You are extremely hard on yourself and leave little, if no room for yourself, to be human. You are beautiful, smart, successful in your career... have a great home, a son, a man who you consider to be 90% perfect... yet you feel like a great big failure. You know ALL of this, and I'm sure you are even perplexed by why you continue to feel like a failure. You keep looking for your answers, because no matter how with it and together and successful it all appears, you still feel unhappy and confused. So you figure if you are feeling this way, there must be a reason for it... so you keep looking... OUT THERE. You continue to look OUT THERE because all you find IN HERE is sadness and confusion.
Yet as I say this, I bet you feel like "the answer" to all this 'stuff' is always right there on the 'tip of your tongue.' Right there... but just out of reach... it'll flit through your brain every so often... you feel it zip through... then it clouds up again.