Welcome to the Forum. Good questions.
Most scabies in humans is caused by direct contact with another, infected person and because sex involves contact between humans, scabies can be transmitted through sex. It can also be transmitted though other forms of contact between humans and even thorough contact from sleeping on sheets or in a bed which a person with scabies slept in before you did. there is a very good description of the illness and its management in Wikipedia.
Typically it takes at least two weeks after infection for scabies to become symptomatic. The infection occurs and then the symptoms occur as the infected person begins to develop an immune response to fight the infection. For the same reason, it can take a week or more after treatment for scabies symptoms to improve.
Humans and dogs can each have scabies but the types of scabies that humans get rarely infect dogs, just as the sort of scabies that infects dogs rarely infects humans.
I hope this information is helpful. EWH
Mange can spread to human but mites dies in a couple of weeks. But am scared that i spread human scabies to my dog. I always hug my dog after coming home from work and he sleep on my bed.
In general, the scabies mites that infect humans are not transmitted to animals. If your dog had gotten scabies from you, I suspect that a flea shampoo should take care of things. EWH