If I might step in as a Guy(straight) that has had 10 +- 3sums in the last 5 months with wife and a female friend.
Your guy sounds very much in a position I found my self in. His imagination of how thing would happen verse how it did messed him up BAD in the middle of it and he couldn't reset.
Example we had a partner that was so tight that it took me so much concentration to keep from cuming early that it made my wife feel ignored. It was not tell 3 days latter when we got to finally talk it out that she forgave me and understood for the next time.