He certainly sounds like he is very anxious. It also,sounds like your patients is winning. He may have had to "be in charge" to survive and you may be the first human who has treated him well.
I would guess that this is going to take a while, but your are on a positive road. Being aggressive back to him will not work and will reinforce that behavior in him. It sounds like you are doing a good job with this pup -- meanwhile, don't turn your back
Keep us posted!