My H was very suspicious of him and I can understand why now but I have to honestly say that when I was first considering leaving he was saying things like...you need to stop and really think about what you are leaving. Consider the things you first fell in love with. Think about your children. This may be a big mistake...and so on. Just the way it worked out. the person he was so suspicious of was on hs side the whole time.
I will just say that you may or may not be right about your EA -- he probably knows he would look like a slimeball if he didn't try to play the "good cop" role and attempt to get you to reconcile with your H. Then again, maybe he really was on your H's side. Regardless, the bottom line is that EA's are devastating simply by their very nature of emotional connection (which is much stronger than the physical, and as a result much more painful for the spouse witnessing it). It doesn't matter what the intentions of either party are -- the fact that you are relating/communicating to another person of the opposite sex in ways that should be reserved for your spouse is a huge breach of spousal etiquette and of trust. You ask if you should stop this "friendship" in order to save your M. Personally, I think the answer is obvious -- don't you?
If you really want your H back and to have a healthy M, you have to end this friendship for good and take the risk that your H might not come back anyway. It is a large gamble, but it is an absolute necessity if you want any chance to reconcile -- your H has obviously said as much.
I'm sorry that you're here and that you're hurting so much, but I admire that you are willing to give up your pride and be humble enough to admit to H that you want to come back and work it out. I don't think my W will ever be willing to do the same. Stay strong and true to yourself, your H, and your M. Things will work out for the best in the end, and no matter what you will be a stronger, better person.