You are bending a line you shouldn't even be approaching. I understand being lonely and unsatisfied whilst still married.
For me if you are in a R you stay and work on it. If that's not possible you end it. Having an affair should not be an option. Especially after being hurt by one, yourself.
I think that you think that the knowledge etc that you picked up here and on your journey will prevent you from crossing that line. It should but I wouldn't count on it.
I am glad it has given you the insight into how it could happen and even how it happened with H.
And my 2x4 is that I don't believe you are in a good enough place to even look at that fire, let alone play with it. You need to tell OM clearly that you wish no further contact, because you are not a cheating woman. And yes an EA is cheating.
Good luck. Thanks for your open honesty
R 25 years M 14 years S11 & S13 Working on it alone since Oct 2014 M in trouble a lot earlier (~2 years) Feb 2016. 1st R chat in a yr. Next R chat Aug'17 Still together