My pitbull/rot puppy is 14 weeks and often very sweet and playful. He is incredibly friendly and affectionate on walks. He has a fondness for women and all other dogs. He is extremely submissive to other dogs at the dog park. He shows this in play, often times falling over on his back, exposing his belly to them. I feel like in training I've made good progress with him: he learned to sit in the past week, and now sits as soon as I start to prepare his food bowl. Tonight, I wanted to work on 'STAY' which took a little work, and is not yet a learned command. I had him sit, and I placed the food bowl about two feet away from him. When he lunged for it, I blocked him with my hand and had him told him to SIT/STAY and would move it closer. He got sort of wild barking and contesting me after a few times (he's not food aggressive). I put the food bowl out of reach for a few minutes. We eventually got it right. He sometimes gets in these modes where he is seemingly aggressive, challenging me in a way. Barking, growling a bit, hopping, or lunging at me, nipping at my hands/arms/face (if he can get to them). I tell him no as calmly as possible, hold his mouth shut if he bites/put his lip against his teeth, order him to sit (he sometimes listens) or if all fails I will pin him to the floor....how do I show him that I'm the Alpha? I put him in the crate to chill out because he was going nutso.