BH here.
For me it was not a single word, event or anything in particular that helped me. If I am being honest I still have doubts about her love for me and her motivations for R. I don't know if I will ever be able to look at it this way. I had to learn to be comfortable with a certain amount of doubt and because of that there is a little part of me that I probably will hold back forever.
The bond is there, but I don't perceive it to be permanent (Til death do us . . .) any more. I have to hang onto to that for my own safety. No amount of words, actions are ever going to change that for me. It is my new normal and I have to learn to accept that or leave the M.
You are never going to convince him otherwise if he chooses to believe this. You might know this to be true, but betrayal has a way of teaching you that you can't take things at face value anymore. It is damaged, it is just less naivete and that is not a bad thing for an individual.
Also forcefully trying to convince him what he believes to be true is going to do more damage to your relationship than any benefit you will derive. It is HIS truth. Try to see it from his perspective and empathize. Trust me if he is anything like me he isn't happy about this new normal either. I resigned myself to "you have to play the cards you are dealt."
I have also settled into "I can't control her," made my plan about what I would do in the future in a few key situations. I could see myself being alright in each scenario so it took some of the fear of the unknown away.
Rebuild the trust first. Then it is a matter of being consistent for a long period of time. If you worked on yourself and these things are genuine they will be taken as that eventually. Provided he feels he can trust you again.
If he can't he needs to address his insecurities on his own terms. If you are looking to be absolved (not saying you are it was in my case) he can't provide that for you nor should he. Once my W understood that she stopped pushing me seeing this "her," way.