I think you should continue as you are. I wouldn't offer words of affirmation at this point unless they are heartfelt and genuine. I think at this point he knows what he will be missing without you in his life- now he needs to FEEL what he will be missing. You are correct that the A will start to lose its luster as the fantasy he's envisioning in his head doesn't play out as he expects. The fact that the OW has a child that takes time away from him will start to get old in a hurry.
Don't second guess yourself for exposing the A to the OWs husband- it will help to speed up the end, despite what it appears currently. Affairs are very selfish things, and both parties involved are selfish themselves. Both want what makes THEM happy, not what makes their A partner happy. Of course, they don't see that yet- they think they want their partner to be happy, and that their A partner is only wanting the best for them as well. If that were really the case, then why would they be putting the other person's spouse and children through this awful experience? Once the fog is lifted, they will only be left with a tenuous relationship between two very selfish individuals. That's when reality will begin to set in.
On another note, I wouldn't ML with your H if he try's to make a move on you. It's not fair to you, and it will only allow him to eat more cake. I'm not suggesting that you are of the mind to, but just a reminder!
As you are aware, affairs are addictions. His brain is pumping chemicals that are encouraging you H to pursue this woman at all costs; that she is now his "soulmate". At the same time, his emotions are pushing him away from you. Picture a defiant teenager, disregarding his parents to go out with a girl that everyone else sees as a bad decision. You can't argue logically with that teen - they will have to come to the realization on their own. In fact, the more you push against them, the more you feed their "us against the world" passion. Instead, you must let them fall flat on their faces. As sickening as it is, you just have to pull away completely and let their R run its course. You'll have to be there to help pick up the shattered pieces afterwards....
