If you simply don't give him anymore money or booze, he will visit eventually give up on you. My nextdoor neighbor has a son who used to come to my door asking me for money. My stock answer to that is "Sorry, I don't have any." I did used to give him a beer. That got old and I don't anymore. When he saw he was wasting his time asking, he gave up.

I don't think the letter is a good idea. You're making it complicated. Keep it simple: "Sorry, I've got no cash in the house." "Sorry, you can't come in to visit because I have to lie down now." The less words exchanged, the better.