I am so sorry that this has happened to you, and for the loss of your animals. I'm sure that you are feeling angry, frustrated, and fearful of what he will do next. It sounds like you are doing everything you can to take care of this situation.
The authorities are rather slow when it comes to dealing with crime in regard to animals. Unfortunately, I know this as we lived in a neighborhood with a guy that owned pitbull dogs that he allowed to roam free. They tore up property, killed people's pets (including one of our cats, and if I hadn't been outside 2 other times, all of our cats), and were not people friendly or trained in any way. Animal control had to "catch" them outside their yard (and they always took at least an hour to show up) or have pictures of them out to prove that it was their dogs. He threatened to kill other neighbor's pets if they called animal control on him. When animal control finally did catch one of his dogs out, they set a dog loose on the officer as he was leaving the yard and he had to beat it off of him to get out of the yard. They took that dog, but they just get more as each one is taken. One of the officers told me that they have a slew of fines (not paid) for other dogs (that have since been put down by animal control) causing the same issues. Every time they go to court they are a fined a larger fee. We have since moved.
Hang in there, justice may be slow, but it will come if you keep good records, keep calling authorities, and stick it out.
I would definitely set up some type of camera and try to record your yard as he seems like the kind of person that will do this again, and again, and again...
I know you are not looking forward to having to deal with a court case, but make sure you rake this *bleep*s arse over the coals so that hopefully next time he might see some real jail time (which he deserves) and be separated from the decent members of society, and your neighborhood.
Good luck