Can't help you on the camera advice, although I'm sure others here can. (Good idea, though!) I CAN tell you that you badly need to do several other things if you have not already:
Contact an attorney and have him/her send a certified letter to the Chief/Sheriff about your neighbor being a certified whackjob;
Get the Restraining Order. No, it won't do much good, but it is one of the "hoops" you must jump through;
Make sure you have a "paper trail" with the LEO agencies involved. Do not allow them to blow it off...tell them firmly and politely you want reports written and get case #'s and officers names. If a polite request for these actions does not get you some reports, etc. request to speak to Supervisors up to and including the very tippy-top if necessary. One or two reports is NOT a "paper trail".
Remember that if this guy finally explodes and you have to use force to stop his actions, the first question they are going to ask after you tell them about all the past "problems" is if all these accusations are documented. (If it ain't on paper, it did not happen!) The absolute last thing you want to have to say is "Well, no, I didn't want to bother the police" or "No. I didn't think it would do any good" etc.
Do not wait one more minute to begin...when you are standing there looking at a dead body, it will be too late!