PET TRAINING CENTER

My dog is a shepard/pitbull mutt, 7 yrs old. Now I have a child, who's 2. As he gets older I am worried about him climbing out of his bed and coming into our room, only to awaken our dog who may be aggressive toward him (he sleeps at the foot of our bed). My dog is fairly well behaved but recently he has shown flashes of aggression toward my son and my wife on occassion. Its usually when we try to keep him away from the "pack". We often keep him behind a gate in the back room of the house, so my son can run around the house during the day. Dog hates it. When my son is gone or sleeping, he's free to roam as usaul. However, my dog is strong and quick, and easily escapes through the gate. he's become increasingly defiant. Question 1: how do I keep him from approaching the gate? Scat mat? indoor fence? remote shock collar to punish his escape attempts? Q2: As far as the nightime concern, should I force him to sleep in the back room? Or should I leave him in our room, but in a large crate?