My ex boyfriend and I work in the same industry. Essentially he accepted a job working for someone who screwed me over. I asked him not to take it, he agreed, but the next day called me at work to tell me he took the position, and I was so furious I broke up with him. Part of me understands, the money is good. The other part of me is enraged and hurt, and betrayed. Did I overreact? It would be our 3rd time breaking up, and probably the last. I am so incredibly sad.
LemonVibe 
Block him from all social media and move on. Don’t contact him and don’t feel sorry. No amount of money is worth hurting those you love and respect. He obviously did neither. Remember, the best way to get back at a ex is to move on and live happily ever after without them.
I sounds like there is other stuff at play here that affected your relationship besides this insident since you’ve broken up in the past and got back together, so it maybe for the best. Take some time to yourself, and if he asks forgiveness and you are ready give it to him, it may give you some closure. Remember, you can still forgive and not be required to get back together. It’s hard to get away from something your use to, but allow yourself time to be on your own, and things will work out.