Ok, little self work here... what is it that is eating you with this ... the fact he is slowly inching that bandaid off and you are at a point you just want to rip the darn thing off and be done with it? ... I get that feel here.
I think its honestly boundary time. Stern direction from you, if you do not need/want the first aid kit, set up a time and let him know .. you also want a list of the rest of the things he 'needs' so this can be done with once and for all .. as you said .. your place is not the pick-n-pull. Or ... maybe this is an item you actually will need, with as much home improvement things as you have done .. you might need this in an emergency and it will be gone, or you will hav eto replace it.
Boundaries ... they need them it seems, heck its almost like they beg for them. I think its time you set this one, he chose to leave and have his own place, along with that comes responsibilities.... feels like he is window shopping your place and seeing what he can cram into his new one.
