I'm confused if you want him back or not. He made contact with you first, albiet through email. So now what? What are your goals?
Just to clarify, email communication has been ongoing. I have replied, in a cordial manner, as needed to communicate about joint practical matters.
He would have to make substantial changes for me to consider returning to a romantic/marital relationship with him. I think it is highly unlikely that he will do that work. So, I won't say 'no way', just highly unlikely.
My goals are: #1, vacate the marital home and protect my financial well being.
#2, (to the extent not inconsistent with #1), inform H of my departure in the way most likely to motivate H towards some self-examination.
I haven't decided exactly how to do that. Most likely it will be shortly before, or upon, his arrival home.
I am not planning to say anything about his pursuit of OW. I had already decided to move out before I was aware of anything like that. OW was just more on top of way too much already.