I am ignorant about how things function in the US, but I did have a friend in rural Georgia which taught me that things function in their own way in that state.

I would say that you could call the police to investigate, but tell them on the call that you husband seems to be paranoid and irrational. Say that if this gets worse you might fear for your safety and ask them for mental health contacts in your area. I'm assuming that in a country area official people know each other personally. They might recommend a psychiatrist who could come out and talk to him, or even come out and pretend to look for the hidden cameras themselves.

Seems to me that in most country places things work by personal contacts. If you are being woken at 2 am, you need so support so that you can keep your own mental health together.

If you've known neighbours for 25 years, perhaps they can help you deal with police or psychiatrist so that you find someone sympathetic and trustworthy. If you don't get someone sympathetic on the first call, try again.

Depends on who you get. Some police are very sympathetic to mental illness. I've had kind sympathetic police arrive on a regular basis when I had a neighbour who was delusional.

Good luck - this sounds sad for you and very exhausting.