I also feel that you're possibly not being straight with us on here, or with yourself.
It's either what you said originally, which was that you thought you were happy and compatible before you met the OM and the affair either brought about your dissatisfactions with your partner or caused you to acknowledge those which had been latent - or before the OM, you weren't attracted to your husband, couldn't have fun with him and couldn't talk to him and the affair was a symptom of that and not the cause.
You've also said you have to work with the OM and so you don't have to experience personal contact to hear about what's going on in his life, or for his presence still to affect you and your husband who also has to be in his company.
It's puzzling that a year and a half of therapy with several practitioners hasn't given you more self-awareness or understanding of your issues, or more empathy for all the other individuals in this story.
If you're not in love with your husband and don't respect him, it doesn't much matter whether these feelings were never there or only departed on the arrival of the OM.
What matters is that they are not there now. Reading your posts and how you describe your husband, it looks massively unlikely they will ever be there. That might be a result of your own sabotage or fundamental incompatibility/poor couple-fit but what's done is done and you'll both get over it if you part.
And he really will move on with his life you know. You aren't his 'one' and quite obviously, he'll be happier by himself or with someone different. You've seen that happen for the OM after all, who you say is in another relationship.