Is it normal to feel guilty for the littlest things?

Telling him to stop moving stuff around is not going to change any thing, as you have already found out. Might as well save your breath and frustration. Many times they use the same hiding places again and again, making the search a little easier. And you might consider locking certain objects up, such as your sunglasses, the good scissors, your key ring, etc. If he's moved a box of Kleenex that has less serious consequences than if he's put your winter gloves in a new place.

If it helps any, for many persons with dementia this is a temporary behavior.

I think it's perfectly normal to feel guilty about losing your patience. I think every caregiver has been there and done that. Don't beat yourself up, just try to recognize that you're losing patience and walk into another room or go get a drink or step outside until you calm yourself back down.

Dealing with loved ones who repeat themselves can drive you crazy. My mom did that and I'd lose my patience too. Of course, she couldn't help it, but that didn't really make it any easier for me to hear the same question or comments over and over again. {{{Hugs}}}