My husband used to use my sewing scissors for a lot of things many years ago (his mother always bought cheap scissors and I guess he never really thought about it). Then fate caught up with him :XD: and he BROKE the blades of my sewing scissors that he'd borrowed w/o permission to cut pieces of cardboard. Yes, you heard right, cardboard. I think he knew he was in deep ... stuff... anyway, I shamed him into getting me new scissors (I gave him a list of stores to look in, I can be nice or I might still be waiting for those darn things). He walked in with Ginghers and has never touched them again w/o asking.
A serious discussion is probably in order if your hubby has boundery issues. What if you had reached in and cut yourself on the open blade because he messed it up? My husband is far from perfect but we drew boundery lines a long time ago. I ask to poke into his tool area and borrow his stuff and he returns the favor. I always had my scissors and cuttors hanging on a pegboard in plain sight (even when the kids were little, they knew never to touch) but if you are worried about safety, use a lock box.
I have never had the urge to keep a stash of candy so I don't really know why he rummages. If he's looking for treats, have you tried hiding a treat on his pillow or in his lunch periodically to maybe curb his hunting instinct? It works for the cats. :-)