re: I need some advice about my dog

You have to put him down for the safety of your child for one. And so you don't get sued when he hurts the wrong dog owners dog.

I didn't read all pages, but I would recommend a harness instead of a collar on walks...if he tries to bolt after another dog, the harness will pull his front end off the ground immediately and he ain't going nowhere.

I had a male great Dane rescue who was super aggressive to other dogs, blinded one (in one eye)and killed another before I took him. I had him cut, (which did NOTHING to counter his aggression toward other dogs) and kept him on a harness during walks which also helped keep him from walking me.

He never showed aggression to other people, though, so I never worried about that.
One day, a teenager jumped my back fence to cut-through to another subdivision...not knowing me and the dog were right there. The dog was on him in a flash, but only took him down by the shoulder/arm and stood over him, hanging on to that arm the whole time, no permanent damage done to the kid, but more importantly, the dog didn't give that "psycho" look he had done with other dogs...the "killer" look you were talking about. The dog was protecting me and his yard, and was pretty damn diplomatic about it looking at it in context.

I wouldn't equate aggression toward other dogs with aggression toward humans. Just keep him fenced in, and order him a harness, you'll thank me.