Hi read your thread and in all honesty not sure where to start.
In short you are doing the right thing because whilst lots of people live uncoventional lives and have all kinds of relationship set ups the key to them being happy is that they are consensual. In your case your h wants to live his life in a way that is at odds with what you want. It sounds like you have given him a great deal of space both literally and emotionally to work through this and "come back" to you but it has been to no avail.
I wont comment on whether he has been selfish and cruel or if he comes across as a good man because when you think about it doesnt matter because his choices have made you unhappy and its no way for you to live.
My situation is different , my xh left us for an ow almost 2 years ago , its been quite a journey recovering and working through everything with some difficult stages to get through. However you will get through and truly you will be happy again even though that may sound unlikely now.
Also like me you know you did everything possible to make the marriage work in spite of what was going on so you will always know that and in the long run it does help.
It is so hard to let go of the future you assumed you would have especially after such a long marriage but soon you will realise that actually a future free from the kinds of dramas you have to deal with for so long is far more attractive.
In the meantime just take it one day at a time and be kind to yourself