There are many cases where the BS becomes a WS down the road. I think you are playing with fire here and you need to back up a bit. I think that the only reason that this EA has not progressed further is because of this forum and all that you have read on the subject.
I think that this might be a bit of a cry for help from you. Kind of like when someone talks openly about suicide. It usually means they want someone to talk them out of it.
I know this AP makes you very good. THEY ALL DO!!! That is how A's start. If they made us feel like s--t, well we would not be attracted to them.
You have too much skin in the game. You have blood, sweat and tears invested in saving your marriage and keeping your family together. I can read the justification and rationalization in your words. You are already making excuses as to why it's just "innocent" right now. It's not. This is how these things start. Just an "innocent friend that makes me feel good".
I think you need to really step back from this and make sure you mark your lines in the sand with concrete.
M-42 W-40 S-12 D-10 Together-13 years Married-10 years Separated-6/2016 ILYBINILWY-7/2016 EA-4/2016 (best guess) PA-7/2016 (best guess)