IMO … At this point, it is too late for adverse consequences to change the behavior of the dogs, permanently. The problem is that they have gotten their jollies far more often than they had the consequences. Animals actually become more relentless in their attempts to hit the joy button when results are inconsistent - studies prove this.
This was studied especially where wildlife are invading towns, going after garbage bins and cooking smells. Some part of the animal instinctively realizes that it’s like a slot machine - unless you keep pulling the handle, you will never get what you are looking for.
For the squirt guns et. al. to work, you would have to make a full-time job out of it and hit them every. single. time. Every hour, every day, every night. Without fail. It would take a long, long time for them to realize this is not changing. And even after you think they have finally given up, at some point they WILL try again. This is animal behavior at it’s most basic (people behavior as well, actually).
Your neighbor will be no better. Perhaps if there is some way to prove to him that you can sue the bejesus out of him and you will … the neighbor gets lawyer letters with large sums printed on them … otherwise, the neighbor is as trainable as the dogs. Not trainable, too long already without consequences he cares about.
Trap & remove is probably the only solution. If you trap and remove, do NOT take them to the local shelter. They’ll be back. This is not your neighbor’s first rodeo. Keep in mind that your neighbor is far, far more experienced than at this than you are.
Take them at least 60 miles away to a shelter or rescue. 100 miles would be better.
And never speak of it to anyone. Ever.
Good luck.
[Years ago, one time in my life, I had to invoke the 100 mile rule for a neighbor’s invading pet that was doing physical harm to my pets & property. Neighbor was spoken too, etc., no change. Neighbor was not caring for this pet, and that was why pet was on my property. But not forever. I had to look out for my own first. Neighbor’s pet was turned over to where it would receive better care than it got from my neighbor … 100 miles away. I had a plan, and it was executed, problem solved, honestly everyone was better off including the invading animal.]