I have no advice and am in no place to give it as I have my own mess to clean up but just wanted to say that I'm so sorry.
Of course I'm not the BS so it's hard to put myself in his shoes but I would hope he would want to R. I am headed down this path soon and have no idea what reaction I'll get so we may become great friends in misery together.
I think the fact that you have never cheated before, if he believes you, is a valid point, but that's just me. I've never cheated prior to my affair either but for me I was with my AP for most of last year carrying on. I'd say what I did was worse if there was a sliding scale. It all depends on how a spouse reacts. One will accept a wife that shows remorse after having several affair partners while another wants a divorce over one inappropriate kiss. You never know, so I guess it's best to never go down that path. If only we could rewind time and have a do over.