It looks like you are exiting the denial stage and are moving into the anger stage. This is part of the process you have to go through. Unfortunately there are no short cuts. I know you don’t believe this now but in time you will adjust to seeing your son less. You will see him less but the time you spend with him will be more meaningful and fulfilling. It’s hard to see now but in time you will understand.
It doesn’t make sense to the LBS how they are willing to give up half their time with their children. We have seen some here willing to give them a way. That’s how unhappy they are right now. Only time will tell if you were the sole reason for her unhappiness.