It is hard to let go of wanting to celebrate their bdays...we have been in the habit for so long. I may be in the minority view, but I say if you treasure your memories, and consider him someone you will always care about, then why not give him a friendly card. JMO. YOu have to be true to yourself, first and foremost.
I wish I had more comfort hope. All I know is, you are a lovely person, with a bright future, who is just currently going through a rough patch.