GWN,
Nice email, but I would change it a bit because I've been where you are now and it's going to go right over his head because they can't focus on a of written words.

If it were me, I would do the following:

1. remove the 2nd, 3rd and 4th paragraphs. You will get an opportunity to say all of this to him later. Right now, it's strictly business in getting the boat and his belongings removed.
2. You say that you've already made plans for Saturday...are you giving him permission to come into the residence and take his things? Don't say take "everything"...he just might leave you w/nothing in the way of furniture, etc. Just say your belongings or things.
3. If he doesn't change his mailing address, just place "return to sender" on the mail. You do not need to advise him again after your email.

Keep the email short and sweet and business-like for now.

Sit quietly, the answers will reveal themselves when you least expect them to.
The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.