What i have heard is that they're not doing it for sexual reasons, but doing it to show dominance. You must teach your dog that he is at the bottom of the pack and not the top. A tip i've read in training books is to pretend to eat their food.
He will try to mate with her, stand up on her back & hump her. If she is not fixed she will get pregnant.
Yes. Only the testicles on the male have been removed, not the penis. Penetration will still happen, as the male dog can still maintain an erection. There is just no sperm production. Indeed, neutered male dogs can maintain an erection, penetrate a female and actually achieve orgasm, and will "tie" with the female. Most neutered males are less interested in sex due to lowered testosterone levels, but still capable of all the actions. They simply do not produce sperm and cannot impregnate a female.
no
he should get fixed
No
Even if a female dog is fixed, if she is on her period, there won't be blood, but she will still give off the nasty smell and that could possibly attract the males, yes. Sometimes though, a male dog (or MAYBE, female) just gets overexcited and, well, you know the rest :D
Get her fixed!
no. if a dog is fixed they can never become unfixed.
It's a dominance thing; the humper is showing the humpee who's boss-dog.
Uh.....huh??
Yes. It is just like how after the first sex, a human can get pregnant.
A male dog may hump its female owner as a display of dominance, excitement, or as a way to release pent-up energy or stress. It is important to address this behavior through training and proper exercise to prevent it from becoming a habit.