Getting tied 5 times a day is fully believable. I've done it with one dog (there was a bitch in standing heat in the next room) and I've done it with a pack of dogs (none stop tied for three days). *BUT* Seven years is not believable. After both of those events it took a week to recover. I was swollen, inflamed, bruised, scratched, and sore.
It should also be remembered that some species (canines in particular) can lactate purely on psychological stimulation.
Gynecomastia is a thing. Men and women both can have enlarged breasts that drip fluid (not milk) due to many factors. Mares can have it from grazing on the wrong plants. But testosterone would be more likely to prevent it than cause it. As for other factors involved in a complex sex life, who knows?
I've pulled a pack and once the first dog mounts you, the rest is history. Males in general have a drive to displace other males in the competition to breed. Just putting a little scent from another male dog on yourself will crank a new dog's libido by several notches.