Sorry for your pain in this. I too found an EA that he swore was just a friend/work thing. He promised to curtail it and I trusted and believed him. Stupid me. When he told her it was going to be only business communication, she shows up all teary at his office, cries that he is her best friend and cannot live just being business associates. He said OK to still being friends, but I could not know. As soon as he agreed to take it underground she knew she had him ripe for a PA. In 6 weeks she had him in her bed for a 3 month PA.
This OW in your life may be playing your H right into her hands. I just wish I had bitched up, not trusted them to do the right thing, and put an immediate stop to it. Or, he would have been out on his butt.
Married 30+ years
2 young adult children
OW single 20 years younger
Together trying to R
Freedom's just another word for nothin' left to lose