What to Do?

I've been wrestling with a problem now for a week or so. If, and I'm not saying I have, but if I decide to put myself wholeheartedly back into working on my marriage, I'm not sure just how honest to be with W about my relationship with J, nor am I sure what to do with J.

W has agreed to let me have a friendship with J. J wants to have a friendship with me. I want to have a friendship with J. However, now that J and I have slept together on two different occasions, it is a bit more complicated. J and I enjoy our time with each other and would both like for that to continue. W, of course, would be devastated if he knew about the intimacy that J and I have shared.

Questions abound, yet I have few answers:
Does salvaging the marriage require me to completely cut off contact with J? Dang it, I fear the answer is yes.
Am I willing to completely cut off contact with J? So far, no.
Could I go back to being just friends with J? I guess, if J wanted it that way, but if he wanted more I would have a really hard time saying no.
The logical, rational side of me sees that J would not be a good long-term match for me so why on earth do I keep wanting to be with him, and how can I continue loving him sooooooo much? Boy, this one is the one I really don't have an answer for right now.
If I decided to wholeheartedly work on the marriage, should I tell W the rest of the truth about my relationship with J or leave it at what he already knows? I'm not sure on this one, but my instincts tell me that there would be no good purpose served by telling W, that it would only hurt him further.

Interestingly, I got a phone call yesterday afternoon from someone who just may be throwing me a lifeline, a way to get some more help on dealing with this whole situation. I don't know what the chances are that it will pan out and don't want to jinx it by saying too much here, or anywhere else for that matter. I'm just praying to God that if this is the lifeline I need that He opens the way for it to happen.