Mandy, You have tried to maintain a civil relationship w/the ex. I think you are very wise to step out of the equation and if your son and the ex should communicate, it will be on their terms. Your ex is still acting out and quite frankly, he may never grow up. Your son is more mature than he is on any given day.
I do hope that you and your son have many plans for the summer and can enjoy each and every day. I know your son is hurt by his father's crazy behavior, but life does go on and w/you there by your son's side, I am confident he will be okay.
Please take care of yourself.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.