I think he needs some watch dogs inside and outside of his garage and also dig a moat around his whole house.
Seriously, why add chains, a loud horn and locks like that and even keep the opener, either get a new opener system that works correctly OR remove it totally and lock it by hand. Keep your opener inside the house, not your car and get one of those numbered wireless key pads installed, you enter the code and the door opens and/or closes.
Dogs wont do anything in a situation like that, they'll just get shot. Would not want to place a pet at the front lines of danger. When someone wants to break into a home they're there to cause the maximum trouble possible. There has been cases of people breaking in to homes and putting any small pets in the microwave, setting it to 99:59 and leaving after trashing the rest of the house. Some people are psychopaths.
I've since got an alarm system and have stickers everywhere so I'm not as worried anymore. Only thing I need to do eventually is add cameras as well. I plan to turn the garage into a shop so I will need it very secure once all my tools are in there.