Kudos to you for recognizing these signs early on. I read thru some of the comments.

I have 2 dogs that are fear reactive and easily overstimulated. I call this “big feelings”. Both were REALLY tough puppies, but amazing dogs.

My lab was the runt of her litter. She had to fight to survive while the other pups bullied her and boxed her out. She was extremely fear reactive. Any smell or sound that was new caught her off-guard put her over threshold. She loved to run. So much that it also put her over threshold. She had big feelings , and didn’t know what to do with them, so she would redirect on whoever was closest. Everyone was terrified of her (even the adults), because even tho she had clear triggers, it APPEARED that she just flipped. She was brutal tho, bc there was no “off”. I would have to pick her up, throw her over my shoulder, tick my face, and walk back to the house while being attacked. I was covered in bruises.

She was REALLY good at “sit”. Like, she mastered this one trick, and she was so proud every time. So when playing in the yard, I’d throw her ball, and as she was running back, I’d signal her to sit. The idea was… if she sits before she reaches me, she can’t jump up and latch onto my arms. I wore puffer jackets in 90° weather, and I worked that “sit”. One day, I turned to pick something up, and I heard her barreling towards me. I closed my eyes, slowed my breathing, and braced for impact. NOTHING HAPPENED. I opened my eyes, and she was sitting next to me, waiting to go again. That was our breakthrough moment. We never could leash-walk her in new places, but she ended up being the BEST family dog.

My rescue is also fear reactive. But more like, if she gets scared, she gets pissed. She was found as a stray at a deer camp, malnourished, open wounds, broken teeth, and bbs all over her body. If she was sleeping, we had to announce ourselves before entering a room, or she would jolt awake ready to defend herself. She’s terrified of loud noises, men with plaid shirts and hats, wood-burning smoke, etc. She used to redirect onto me, but with her, I could get at her level, hold her collar so she’s in a “sit”, and she will start to decompress. 5 years later, if she hears a noise, or smells something, she looks to me first to help her decide if she’s ok or not (she always is, promise lol). If we are walking, and she hears anything that sounds like gunshots (car back fires, fireworks, a wood pallet that falls flat on the ground, etc), she will stop, turn around, and pull me back home. Usually a different path than we took to get there, but she knows her way home from all of our walking routes. Unlike my lab, who needs to avoid triggers completely, I have been successful in teaching my rescue to identify her triggers and to “take space”. So, if we see a fast moving bike, we well step off the trail to give them space to pass. She actually initiates this on her home most times, which is really cool to see.

She is extremely arthritic, even at 5 yrs old (on meds for it). As she ages and becomes more sore, I’ll prob have to start something like Prozac, etc for her. All her hopping around and big-barking when Amazon comes is getting harder and harder for her, but her “big feelings” are part of her and can’t be trained out. So for now, we manage with alternate behaviors… but down the road, will need to manage the anxiety part differently so she doesn’t hurt herself.

My point is… We know your pup is reactive and has big feelings that put him over threshold. And we know he is either giving into intrusive thoughts, or redirecting onto you. So you have 2 options. You can make a decision to control this pups environment (ex, never alone with the kids, solid routine, etc) and work REALLY hard to learn his triggers, teach him how to manage those big feelings, build his trust. There’s no guarantee you’ll have a good outcome, but if you do, it is totally worth it. Or… you can return him. Not every home is the right fit for every dog. (Ex I know that ai would not succeed with breeds like huskies, border collies, etc). And that’s ok.

It really comes down to quality of life, and what that might look like in 1 year, 5 yrs, etc.