I spent my evening cleaning up the mess he made but it will be worth it. Tonight's plan is to start moving things into that closet, which will free up quite a bit of space and cut down on clutter. I'm decluttering as I go, I have a huge box of stuff to drop off at a thrift store but I didn't think to stick it in my car this morning. I'll do that tonight and drop it off tomorrow.
He's also re-roofing the shed. Once that's finished several things will be stored in there, things he wants to keep but don't currently have a "home", therefore are seen by me as clutter.