FBinNY 

The yelling or so-called threatening to mace his dog is a nonsense offense. In most states a loose dog is considered a wild animal, and fair game for any defense up to death if posing a threat.

However, since the police seem uninterested, you have a few choices. You can persist with the animal control people and demand that they either cite him for failure to keep his dog on the property, or even take it away. You can also get the prior incident on record, so any future incident is a repeat offense.

Or you can file a complaint with the police dept, which HAS to take it for the record, even if they choose to ignore it, or bypass them and file with the local district attorney. IME- I've found that DAs (or their office) take people who go to them directly fairly seriously, and will step in to resolve issues (sometimes through threat) when others won't. Lastly contact your representative on the city or town council, if others choose not to act.

It is critical that you get your complaint on the record for the simple reason that officials know that if a complaint of a hazard is lodged and not acted on, they (the town) can be held liable if there's a repeat offense. This financial exposure usually motivates them to make at least a Pro Forma effort at ending threats.