Wakeup, the tears will stop. I can't tell you when but one day you will get through the day without tears, you will be able to walk in his room, listen to his favorite song, fold his clothes, or think about him without tears. I thought they would never end but somehow they do and you will have passed into another phase.
You did nothing wrong. I have a very good friend who adopted her daughter at the same time we did. Just two weeks ago she moved out and moved in with her birth father. Turns out she found him three years ago and has been having a relationship with him since, unknown to her parents. My friend feels like she has been a babysitter for the past 22 years. She can't understand how her daughter could just walk out the door after everything they have been through with her. She doesn't know what to do about Christmas, whether to buy her gifts or invite her over or what. She is 7 months pregnant, unknown father, has only part time job and appears she has just repeated the cycle of her birth mother. Sad isn't it?
We all did what we thought was the best for our children. We adopted them and loved them and gave them every opportunity and sometimes they turn their backs on us so easily as if we were just babysitters.
I think he will be back, just as I told my friend I think her daughter will also. It may not be until he discovers his life is not greener on the other side or until he understands what it means to be a parent himself, but have hope. In the meantime do something nice for yourself and enjoy your grandchildren.