Good luck Pink! I bet he will handle your note with grace and kindness. From everything you have said about him your T seems to genuinely care for you. Personally, I think that the more you are able to courageously reveal to him about your innermost needs the closer and closer your connection will become. The one complication may be if he does not do physical contact (my T does not). It took me a long time to not feel rejected by my T because he would not touch me at all. Now, I can ask for a hug and he will write on a note "I'm hugging you now" and pass it to me. I kind of wish though that I did not always have to ask , mind you... But it has always been that way that I have had to negotiate for what I need. At least he tries to meet me halfway anyway.
Yes, I think this is a very good step for you. Be brave!