OP
You are going to have to
Change the locks anyway. He's been living with you and 'cocklodging' and he's has form for stealing items from you and selling them behind you back already.
You won't be covered insurance wise for theft in this case.
Change the locks today, I've done it on a Sunday (as key broke in lock) cost £100-120, instead of £80-100 on a weekday, so not much extra.
Then get someone, a friend, or relative, anyone to be there when he comes to collect his belongings. In fact I'd pack his stuff up for him and have it by the door ready. He doesn't have the right to go round your property looking , all he has the right to do is ask for specific items if he thinks anything is missing. He can do that by taking his stuff and checking at home later. Which you can look for in your house (later if need be) and tell him if you have it and when he can collect anything that you'd accidentally missed. Don't leave his stuff outside & defo not in the rain, as you'd be responsible for it if it was stolen or ruined. I'd move it to porch just before he is due to arrive so he doesn't set foot in house.
Get everything about arrangements in text or email and screenshot texts and ta me photos of large ones of his items packed up in (bin)bags.
Definitely don't leave him free reign to go round stealing from or damaging your property.
A make friend of mine did with his ex gf (leaving her to collect her stuff to move out) She poured bleach on top of his hedges at the back, removed shelves from his expensive new fridge, bolts from his DCs beds, bits of his tools rendering them unusable, and stole some expensive presents of his. His TV was scratched as well as hard drive messed with, with his DC childhood photos on it lost. Police weren't interested at all and even taking her to court he initially got a financial judgement and lost it on appeal as he 'couldn't prove' she did it, she simply denied it, despite dates photographic evidence of what he came home to that evening and NDN saying they'd witnessed the damage to hedge was done during 10 hour period whilst he was at work and she was at the house 'moving out'. That doesn't include bin rubbish smooshed into flooring and other unpleasant stuff. (He threw his toothbrush out straight away just incase!)