Man if he's out bragging about it I would have a really hard time not confronting him about it. I don't know the full backstory but it sounds like if you went over with another neighbor and hes a hot head IF anything happened it would be clear who started/did what in the situation. Good luck
High powered Air soft guns work great for situations like this!! I used one on my neighbors dog who used to crap in my yard. Worked for me Sent from my iPhone using Tapatalk
Cant you get a trespass order against him? Then set up a camera and as soon as you see him on your property, take the evidence to the police along with the trespass order and he will be arrested.
Kick his *** sea bass. All kidding aside you need a fence for your dog and your neighbor. I would get even some how though.
Sounds like the kind of guy to covertly sign up with buck masters, that should piss him off for 6 months or so.