I agree with one of the points that Oskar's mum mentions for a dog that loves to chew and loves meat a Kong would be a great starting point. One other consideration is that dogs are intellectual beings and need mental stimulation as well to combat bordom. I wonder what his training schedule is like? Some of the unwanted behaviours you have mentioned could be redirected into desired behaviours, and if you reward the desired behaviour with chewy treats you can start to redirect the behaviours to where you want them.
Dog's do try to protect their "pack mates", if one dog is having a confrontation with another dog, it's pack mates will back up the leader, so it could be possible that your dog sees arguing as barking at an intruder so your dog backs you up.
It seems like you have a desperate need for some professional advise, look for a local behaviourist and get some advice. Unfortunately the longer these behaviours exist the harder it becomes to correct, or the worse it is likely to get.
I will read the forum rules and then ask http://www.dogforum.com.au/members/morgan.html the forum owner for permission to plug my websites - message brought to you by Hyacinth - super mod