another thing he told me is that he doesn't like how he feels that their couple time (cuddling, sex) feels tainted by me. He feels that she is bringing my aura into his bed.
Their sex life has sky rocketed from once every few weeks to once a day. She has typically been a sex negative type person. He even admitted that their emotional intimacy and communication with each other has improved greatly.
Basically he's dealing with mirroring and magnifying. A marriage that chooses to Open will have every crack magnified and reflected back. That's why it is best to start with a strong foundation.
He's discovered all the places -- communication, sex -- where he/she could have tended to the marriage better without you around as a catalyst.
But they didn't. Now you are around, and they do.
Having that mirrored to him if he thought "all was cool before" is hard to bear and it is tempting to want to go back to "not seeing" like before and blame the newcomer (you) for this unwelcome knowledge.
He could choose to dwell on the "lack" from before and feed the insecure bucket. Or he could choose to use this new awareness and step it up and continue to enjoy his marriage more. He could choose something else entirely!
For you though? You could try to offer sympathy since you seem to talk to him and try to be honest and see if that helps make the situation a bit more bearable for YOU. Something like...
"Yes. It sounds like it is very hard to experience that sort of "mirror" -- where all the places in the marriage that could have had a little more TLC before I was around are shining out and reflected back at you. (<---Validate where he is at.)
But I am glad you guys are tending to your marriage and are enjoying better communication and better sex with each other as a result. This is a good thing. You and her are doing good things for each other." (<-- Focus on "togetherness" and his part in the effort to build that up.)
Could always end on a positive. Could choose constructive tone. Could try to feed his secure bucket so he can learn how to feed it himself by modeling YOUR talk as his inner talk. Then you don't have to deal with chronic insecure any more out of your metamour -- at least reduce the "volume" on that.
I tried to help him understand that you can't insulate your spouse from the outside world. Her moods are changed and effected by EVERY personal interaction be they friends, family, or grocery tellers and to feel that she shouldn't bring any of that home is unrealistic. I can't believe he would rather go back to their old relationship style simply because it was unaccosted by me.
That first bit is logical. But the tone
if those were your words to him verbatim? That's "take away-ness." He's "losing" her to other people -- the friends, the family, the grocery store worker. He already suffers too much of that kind of thinking - don't feed THAT bucket by giving him MORE people to stress out about that will "take her away." He already stresses out that YOU are "taking her away" somehow.
Could point him back to where she is WITH HIM so he can get secure in the "togetherness" instead. Could point to him putting in work on his marriage and praise that. Things he CAN control.
Hopefully he gets into the habit of talking to himself inside his head that way -- in more constructive, feed my "I can handle things" bucket type of way and it results in him being more secure and then gets on to putting the work into HIS POLYSHIP.
Are they thinking about a counselor? If he need extra PROFESSIONAL support?
But that bit in bold?
I'm not surprised. The unseeing who now have to see? All the places in the marriage that changed? If even for the better?
Those are places in the marriage he had a hand in neglecting. Both of them. To want to go back to a time where this knowledge was not in his awareness is a common enough reaction. Nobody likes to be called into account (which this kinda is) and be shown where they were lacking.
Some people handle that with grace and move it forward toward improvement without too much extra support. Some people can't deal with that alone -- and experience all sorts of things -- regret, guilt, beating up on myself-ness, etc. They need more support to learn to surf that wave.