Hi, just popping in, and haven't read through everything but thought I would offer my two cents. I have dealt with the exact thing! It gets to be painful after a while when the ex just slowly picks away and grabs items from the house as they need them. I certainly feel that you are within your rights to explain to him exactly what you wrote, that you would like him to pick a date, come by and grab all of his items. It is not rude, your house is not a yard sale.
I said the exact thing to my ex as well when he was doing the same thing. We set a date, and he came by for what I called a "Final Walkthough" That should get the point across. Just tell him you would like to set a date for him to come by and do a final walkthrough of the house. Believe me, there is MUCH relief after that final walkthrough is over, as you can re-claim the house, and feel a sense of relief. Just as a funny sidenote, the things that my ex grabbed on the walkthrough were hilarious!! (apple corer, 3 of our 6 wine glasses, thai noodles... ) And also, if it helps you any, perhaps you could have a friend there while he does the walkthrough, if it helps you feel more at ease.
That should get the point across. Just tell him you would like to set a date for him to come by and do a final walkthrough of the house. Believe me, there is MUCH relief after that final walkthrough is over, as you can re-claim the house, and feel a sense of relief. 