How do I know if my dog would be good for personal protection?

I am interested in determining if my 11 month old male GS dog can be instructed in personal/property protection. I have been reading about bite work, etc, and I feel that I may be too late. I play with him on a daily basis with a "pull toy" he has gone through several rope pull toys, and I am currently using some sort of synthetic pull toy. I am a police officer, and I spoke with a friend from another local agency that does K-9. He suggested that he would get me some burlap to play with the pup. Is there anyway/any product you sell that can let me know if my pup has the "hardness" or "drive" to be a working dog? I have noticed that when he annoys my 6yr old female Rottweiler, she pins him and he submits fairly easily. I think he may be on the submissive side, but I want to be sure. Another example is when I walked into my dark kitchen after work tonight, I didn't say anything, but I walked towards him. He was barking like he usually does when someone comes into the house. The house was completely dark, and he ran away and stopped barking. It was then that I realized that he was scared, I turned on the light to make sure he knew he was in a safe environment. I found him in his crate (I leave the crate door open for him), and he had eliminated in the corner of the crate. It is for this reason that I am not sure if he has the ability to be a protection dog. If I had knew that he was going to react like this, I never would have tried to see how he would react. Can you let me know what you think about this?