Stop Snoring Remedies

I was given Boxer that was about 6 mos old. He’s now around 8-9 mos old and I’m having difficulty in obedience training. He was a stray that was handed down to me by 2 diff ppl. I already knew that Boxers can be stubburn and hard to train, but I’m a dedicated pet owner and am determined to break him of bad habits and turn him into an obedient companion.
“Rocky” stays out in the backyard until we come home from work. He’ll lay on the ground until ur within reach and then he springs up and jumps on u. He knows the basics, etc: “no”, “sit” (as well as the hand signal for sit), “stay”, “toy” and “drop-it”.
I want him to be protective of our house b/c our neighbor has had a break-in and we’ve had a car stolen.
Rocky snores so loud that one time when we came home he didn’t even hear us and I was the one who scared him instead of the other way around. He doesn’t bark unless he’s trying to play w/one of our cats, even when someone knocks at the door, he stays quite and just looks up and walks to the front. I wish he would be a little more aggressive/territorial….How do I go about instilling a guarding behavior in him?