He seems to want to either eat or destroy the postman and anyone that walks past

I rescued my male yorkie rambo about a year ago. He was abused by a few previous owners. When I first got him he would bark a bit if someone walked past the windows and growl if a dog passed. He would bark at the front door whenever a postman was nearby. Over the last year we have managed to correct most of his destructive behaviour but this just gets worse the more we try. Now he tears letters from the door, scratched and chews in the door frame and if we have to open the door to accept a parcel he goes bananas and tries relentlessly to attack the poor guy. This behaviour has now moved beyond just the postan. Now he aggressively barks and growls at anyone walking past and we can’t let friends or family unto the house without putting him outside first. I’m out of ideas and he spends most of his time barking, growling and attacking windows and doors. Not to mention he scares the life out of my chihuahua who is very quite and unphased by the outside world. I’m getting really concerned he might actually bite someone. What can I do?