Hi, welcome to the club that nobody ever wants to join.
SHE NEEDS TO DUMP THIS THERAPIST ASAP. I am shocked a therapist would recommend building a life on lies and deceit.. So ridiculous. Seek one out that is experienced in infidelity.
First, take care of yourself, you are experiencing emotional trauma and will have PTSD like symptoms. Eat, drink water, and rest are essential. Next you don't have any obligation to make a promise and frankly it is impossible to predict the future it has to many outcomes.
You wife's choice to cheat had absolutely nothing to do with you or the issues or problems if any in your marriage. It has everything to do with her and the 100% selfish choice to cheat. If she had issues she could have talked, counseling, separated, or divorced. Instead she choice to lie and sneak around.
Your wife's drinking had nothing to do with the sex. It was a CHOICE, the drinking is an excuse. She didn't get drunk and fall into his lap. There is always prior relationship, boundaries crossed, secret talking, etc. The business trip and drinking was just a opportunity and justification.
I recommend the book "Not Just Friends" by Dr. Glass which can be found on amazon for both of you to read.
Affairs are fantasy land and drug fueled high's. They have no reality or real life. The affair partners lied to each other and said whatever made the other partner happy (hence the drug) to get what they wanted (ego boosts). The "feelings" you are searching for didn't exist and if so the common "luv" stuff is bullshit based due to the lack of real life involvement. Its easy when all you have to do is show the best of yourself and it is never questioned and the worst is hidden away. He probably told her how smart she was, funny she was, and good looking she was and this made her feel like the most important person in the world. And like wise she gave him his ego boost in bed or by other means.
Your wife has issues which are deep seeded. Emotional issues with her self worth, self image, and self esteem which caused her WHY's and the coping mechanisms to allow her to inflict so much pain and justify her actions by minimizing fueled this behavior. Read the book I recommended.
If her boss is married YOU need to tell the other betrayed spouse immediately! You have to bring this into the light she absolutely deserves to know wouldn't you? You have to do this don't rely on your wife or let her know you are doing this. A certified letter, email, in person, phone call. Make sure she knows. She has the right to know what her husband is doing and risking her safety and life.
You need to report this to the companies HR department an official report. Your wife was a subordinate and even though made the choice the guy is a boss and there maybe others or future "victims" and families.
Don't feel any SHAME you did nothing wrong and are the prize in this relationship, you are not broken. Your wife is suffering from an identity crisis. Wayward's suffer self deceit in justifying their selfish choices and finding reason in such flawed thinking is impossible. Nothing makes sense and feels ass backwards.
Read the healing library here. There is lots of great people on this forum we have all been there done that and wished we would have listened to the advice because we always think our situations are different or our waywards are different. Surprising that most all affairs are the same both during and after almost like there is a CHEATERS HANDBOOK.
Be prepared to find out more as the truth unravels and trickles out. The waywards hide and don't want to face what they have done and become. They will try to "protect you" from knowing just how bad it was. This is really just another selfish justification for lying and manipulating the outcome of healing. You need the truth. They need to see how awful of a person they were. The trickle truth is brutal and a form of emotional abuse it will kill the marriage faster than the sex.
1. Total honesty
2. Total transparency and openness
3. TOTAL NO CONTACT, NOT EVEN A KEYSTROKE
Try sharing your story, there are a lot of unfortunately experienced members here that will help you..