[Gnostic Dog]

What a difficult situation you are in, and poor puppy. Pardon me for asking because I don't know his background, do you know the reason for his severe fear/reactivity?

ETA: Not that this is very constructive, but the ONLY time my boy has shown any fear was when my eldest daughter needed crutches for a broken ankle, her appearing on crutches caused Oscar to bark, run into his crate and pee (first and only time he has ever done that). It only happened the one time though and he quickly got used to the crutches. But I guess canes and crutches can be scary things, even to confident dogs.

 

[Gnostic Dog]

I wonder if its PTSD, rather than a genetic? You probably won't be able to answer this question, but do you know if Chisum was dropped as a young puppy. I ask this because dogs do not discriminate between the physical and the emotional, and fear and its manifestations (territoriality, phobias, possessiveness, owner addiction, separation anxiety, dominance, submission etc) invoke the fear of falling.