Nas, I'll tell you what I did and I cannot begin to know if my sitch applies when the sexes are reversed (You know Mars and Venus issues). But when my W was having an affair back in mar. I knew about it before I confirmed it. Afterwards, we were discussing it and my W made a comment about much little self-control and lack of self-respect I had for having sex with her while I knew she was screwing someone else. That hurt!! and bad, because I realized it was true. I justified it in a couple of ways. One, because I loved her and I had "needs" and two, if she was going to have sex with someone, it might as well be with her H because that is how God wants it. But, truth is, I got used for a sex toy because OM was not available. It doesn't feel good to feel used.
I personally haven't experienced in my M where making my self available for sex or for friendship has encouraged my W to desire reconciliation. What I have experienced is that by being friendly, not her friend; has helped me keep from showing anger. That's what she said would make it easier to leave; if I was angry. So I suggest being friendly; but not his friend. Do you know what I mean? Keep the communication line friendly, not necessarily open all the time; but when you do communicate you do it in a friendly manner. It will make it easier for him to return.