I know it's the best advice to give, but it's so hard to follow: don't talk about what he is resisting right now. I keep making the mistake in trying to talk to my H about things he doesn't want to discuss (namely anything about our relationship and future). I get burnt every time, but I'm doing it a lot less often. It makes me feel bad, even though I rationalize at the time that he pushed me into those conversations.
I guess I wouldn't push for faster or more intense counseling sessions re. his affair if he's telling you that there are too many discussions already on that topic. However, that is not to say that you don't have every right or reasonable expection to get answers to the legitimate questions you have. This stuff is just so hard. He sounds like he's withdrawing some and that pursuing him will likely make him withdraw faster and more. I just experienced this yesterday (under Communication "Been Great, he's worse") and I've decided that I'm still digging a pit for our marriage and my shovel is my seeming inability to make decisions without knowing what the likelihood of success is in our marriage.
