Sadly, I am not surprised it has gone like this, OP. I expect you have been spending the last few weeks jumping through every imaginable hoop trying to compete - and losing so much of yourself in the process.
As I said upthread, I suspect this is a different type of affair to the ones we often come across on this board, where there is an addiction to the feelings and not the person.
Affairs that are borne out of a proper deep friendship, often involve genuine feelings.
What never changes though, is that this is all about him and not you. If you looked at that other thread I directed you to, you will also see that, like Abedelia wisely points out, betrayed partners often set the clock too late, when trying to identify when the marriage became "stale". So often, that only started to happen after a spouse has detached from you - and often because of another person in the marriage.
You trusted him that he had ended this relationship, but as you were asking no questions and weren't verifying what you were being told, you have perhaps assumed that if you could meet his every need, this would ensure his detachment from the OW. This just never works. Competing never does work, whereas taking control and asserting your rights has the twin benefit of retaining your self-respect and increasing the respect in which you are held by your H.
I sincerely hope you will see now that the respondents upthread were right, all those weeks ago.
It is hard enough coping with ambivalance after the extra-marital relationship is over, but it is impossible to stay in a marriage while the affair continues.
I agree with others in that I suspect your H is manipulating the situation so that you can look the bad guy who kicked him out. Kick him out now by all means, but don't let him manipulate you or anyone else in your life. Tell everyone calmly and clearly that you weren't prepared to stay in a relationship that was no longer exclusive. Put the responsibility for this where it lies.