Great Danes and Ridgebacks were bred to hunt large animals. Boxers were also hunters, with the additional job of herding and fighting in some parts of the world. All three breeds were used as watchdogs since they are strong and unlikely to back down. Boxers are very energetic, whereas the other two tend to be chill as adults.
So, in short, I’m not sure it matters so much. From the pictures, a Ridgeback seems unlikely to me – but since they are quite rare around here, I’ve only known a couple.
The ridge on Cato is very, very important. It’s a clear sign that he is scared, and acting out of fear. That means he’s not being protective, or even aggressive in its usual sense. He’s being reactive. If he will calmly take treats from strangers, you can try letting everyone you see feed him. However, that might be too much already.
As to dogs, it’s totally natural for a young dog to become reactive if he doesn’t have regular interaction with other canines. If you have any gentle, friendly and confident dogs in your social circles, you might try a leashed walk together and see if you can help him make some friends that way. Letting him interact with unknown dogs is pretty risky at this point, since he might get attacked due to his lack of social skills.
It’s clear to see that he is terrified of the vacuum. I would be very careful there. While it’s great that you’re trying to train him, I would advise against asking him to sit. I know many trainers will tell you to do that. Personally, I think you can get much faster results by using simple classical conditioning. Cato sees person = a treat flies into his mouth.
Sitting in a scary situation seems very unsafe to dogs, as it makes them more vulnerable. Plus, movement is a natural stress-reducer. If you can get him to catch treats in the air or chase them along the floor, that would be best.
Does Cato react to the doorbell yet? If so, it might be a good idea to put him in the bedroom for Halloween, but throw a few awesome treats in there whenever the doorbell rings. I would not let him near any children in costumes. Chances are you’ll have a scared dogs and frightened kids.
I’d give you more ideas, but I really think you need a trainer. In a six month old dog, this behaviour will get worse without an intervention. He’s scared right now. With training, he has a great chance at becoming sociable and confident. If he stays fearful though, and reaches maturity…that’s a scared and confident dog. Not safe.
Here is a link to what might be my favourite dog trainer in America, Emily Larlham. She is not only highly skilled, but also very kind. I think if you send her a message asking for recommendations in your area, chances are she can help you. Good luck, and please don’t let anybody hurt or scare Cato under the guise of “training”.