Your responses have been helpful to me and no doubt to many others.
Try not to let this situation cause you to "react." No doubt it is very uncomfortable...but as best as you are able, I hope you will push through the discomfort. I think you should commend yourself for giving this some thought and sending an appropriate note. (by the way, I would do more than the note.)
You help folks here. Do you have younger kids still at home? I bet you help many folks. Through work, volunteer or otherwise? Ya know, our UPS person periodically stops by and spends a moment talking with- me and I can tell that he is paying attention to my demeanor. One day he told me that it is his "calling" to spend part of his day helping others by paying attention to others to see if he could lend an ear or a word of advice, if it was something he was familiar with. It was very powerful...very touching. He is kinda like a father figure/uncle, etc. to people all over the city...each and every day.
Sure, your son seems to have chosen another path that doesn't particularly include you right now. It seems unhealthy and selfish. Perhaps in time, he will change in mind.
Please don't let this define you. You are a special/unique/intelligent/creative and giving person. His actions doesn't change this one bit.
Life moves on...you continue to enjoy your talents...and others continue to need them.
Wishing you well.