Do I think he should be texting the OWs friend? Heck no!! That should be part of your NC agreement. NC with the OW and anyone or anything connected to her!
Correct. Because physiologically, his brain goes thru the same stimulus if/when he talks to someone ELSE about OW, than it would if he were talking to OW directly. And in fact, even NEGATIVE conversation about her stimulates that part of his brain, and basically sets his withdrawal "clock" back to 0:00:00.
Stimulus is stimulus. As HS says, YOU want to be the one to talk to him. Don't let him talk disrespectfully to you (if he does, just calmly say "We can talk more when you're ready to be more respectful"), and don't let him "pine" for OW. But DO let him be moody around you, and feel like he can talk to you.
It's a tough rope to walk, I know. Maybe this will help:
Husband:
"I miss OW! I can't believe you made me give her up!" = NOT okay
"I just don't want to talk to you right now!" = okay
"She used to make me feel ________, and you never will!" = NOT okay. Reply with "Look, I'm sorry you're hurting, but I'm not going to talk about your affair partner with you, as it's very disrespectful to me and to our marriage. What I WOULD like to talk to you about are things you feel you ened from me, emotionally, that you felt you weren't getting. Can we talk about that?" (or something similar)