My neighbour is crazy. What can I do?

Don't hide out, you are telling him you called the Police by doing so. Get a restraining order against both. Next time he beats her, just ignore both.

The first thing I would do is request a restraining order also I wouldn't put off the thought of a legal firearm depending on what state you live in.

Adopt or borrow a big dog from a shelter and introduce him. Explain that he is a little uncomfortable around violence and loud noises because of his past as an abused animal. He really doesn't like men because his previous owner was one of those childish idiots who beats on defenseless creatures--- as a word of caution. I am obligated to warn all of the neighbors about him as part of the agreement for me to foster him, so I am just letting everyone know. Please try not to make loud sudden noises if possible, and definitely don't make any sudden moves towards me because he is ridiculously overprotective. Otherwise, he is gentle. Knock gently on the door if you ever need to get my attention. Otherwise have a great day!

and that is why i always have a gun within easy reach... anyone breaks into my house trying to hurt me or my wife, theyre getting shot

Start with a restraining order.

Report him to the police again.