I would never ever ever put an ad on Craigslist or Facebook to rehome this dog. If you want an experiment, post again and state he has been altered (neutered) and see the change in responses you get. I still wouldn’t rehome him that way, but it’s interesting to see that responses to the ad will go wayyyyy down, because unscrupulous people would likely do a one off breeding and pass him along to another BYB, creating who knows how many pups that could have the same ending as yours.
Are you actually wanting to rehome, or would you prefer a board and train and just can’t afford it? I’m getting both vibes from what I’ve read.
For me personally, I wouldn’t euthanize, but I wouldn’t rehome either unless a full background check was run, and had an attorney draw up a contract releasing you from all liability after transfer of ownership. But I’ve spent 20 years taking in aggressive dogs that are on their way to euthanasia. My current senior was exactly like your boy, except I got her when she was 4 and they no longer wanted to deal with her aggression to get money from her pups. But it will be difficult, if not impossible to find someone willing to not only take on your dog, but all liability as well.
I’ll be blunt, it seems like you probably handle him with kid gloves, and don’t like confrontation in any form. If I took any of my dogs to a trainer, and they pulled any macho alpha crap, I’d step in and immediately end the session, and tell them their services were no longer required. My vet also knows, and has a big neon note on the front of al my dogs files, that if a muzzle is necessary for any reason (beyond an emergency) that they are to notify me, and I will muzzle my dog. Not only do you need to be a confident handler, you need to be the spokesman for your dog as well. Both scenarios did nothing to help your dog. I’m really not trying to be rude, and I could be reading you all wrong, but when it comes to dogs, I tend to be more outspoken and direct.
If you don’t mind answering, how much did the trainer want to take him for a month? If you don’t want to post, you can PM me.
If your only two options are to rehome or euthanize, I would opt for euthanasia if you weren’t confident in the person you are rehoming to. I would personally demand a full tour of their home and yard, ask for any prior training or trialing experience they had, with proof, and go all Sherlock Holmes on all their social media accounts to ensure they have never bred any animal before. Or have him altered before rehoming to prevent anyone from breeding him.
The behavioralist was correct, the dog will likely need a lifetime of management. My senior is still one of those that requires it, but I have taken her from attacking me and shredding my arms the first two weeks, biting (or trying to bite) any dog or person that came near her, to her successfully living in peace with 4 children and 3 other dogs. She’s loyal, sweet, cuddly, and amazing, and I wouldn’t trade her for the world, but it took a lot of time and constant effort to get her there, and like I said, we still have a lifestyle of management with her. It is what it is genetic wise, so we work with what we have. She does go in public now, she’s walked daily with zero issues, and she still loved to hike with me even though her joints didn’t. She’s the most loyal dog I’ve owned. So there is hope, but it’s a long shot finding someone willing to take on that type of project.
What part of CT are you in? Maybe, if you’re interested in keeping him, members here could give you excellent trainer information that may be the turning point you need.
Good luck on whichever decision you make, and please keep us updated.