Most Helpful Guy
That sure seems inconsiderate of him. More importantly, I'm sorry you are sick and I hope you are on the mend.
He has to be living somewhere, so it's strange he's having his stuff sent to your place. I would recommend with every letter addressed to him, you simply write "not at this address" and put it back in your mailbox with the flag up. His crap is not your responsibility, so he can deal with it via claiming his stuff at the post office.
If I had to guess, I'd say he's using this a some twisted way of controlling you, even though he's the one who split. He gets to go be a jack off, but still has an "in" if he wants to start communicating with you again.
Either way, he's an idiot and I'd write he's not at that address and let him deal with the post office if he wants to get his stuff. If he calls you complaining, tell him to stick it up his ass with his new change of address.