Alfie, I'm sorry if this comes across as blunt but I think you need to hear this.
Stop minimising what he's doing. He's minimising what he's doing, that's what cheaters do!!!
It's not a case of some would say it's an emotional affair, it IS the very definition of an emotional affair:
1)He runs you down to another woman
2)He keeps the exchanges in the relationship secret
3) He meets with her in secret
4) He refuses to accept that the relationship is damaging his marriage
My guess is that the only reason it's not a physical affair is that the OW isn't that interested, she just enjoys the ego stroking and attention from your husband who she has dancing on the end of her string.
She is a Jolene in that if she expressed an interest, he would jump right into the sack with her.
If I could go back in time and catch my husband during the time it was just an emotional affair, I would react the same way as I did with the physical affair. He would be out the door to live his fantasy life with his whore which crumbled within 48 hours.
You're luckier than most of us here, you have the opportunity to stop this before it escalates. You decide, not him.
The rest of us are here because our cheating spouses have cut contact with their affair partners and are trying to make amends. Your spouse is in the midst of an affair so there is no saving your marriage until you admit that to yourself. He needs to experience what he's going to lose if he proceeds on this path.
I'm sorry if this sounds a bit harsh and I hope you take care of yourself.