Just a suggestion.
Assuming he is truly deaf clearly he can read and write.

I am not an atty BUT, a registered return receipt letter, EVEN IF THE PERSON DOES NOT ACCEPT IT, after three attempts to deliver the post office will return it to the sender AND LEGALLY IT HAS BEEN DELIVERED.

I've not done this in years BUT, for a few extra bucks you can send a registered letter RESTRICTED DELIVERY/

,MR SCHWARTS WOULD THEN NEED TO DRIVE TO THE POST OFFICE TO SIGN FOR IT AS WE DO NOT HAVE DELIVERY TO YOUR DOOR

I do not believe in fighting fair. I HAVE LITTLE EXPERIENCE IN LOOSING.
You could also come up with as many small claims court cases as you feel you need where MR Schwartz would need to attend to defend. If, he refuses to come to court he will lopse you then can after whatever the number of attempts is in Florida law-back home it was three letters, you send the sheriff to his home to collect.

MORAL OF THiS POST-you do not want to fight the battle the expect.
We all have read the story of David vs Goliath-had David fought the battle that Goliath wanted, DAVID HAD NO CHANCE.