Independent dog needs some help

(Sorry if this is a long post!) Tl;dr: Dog makes his own set of rules. Doesn't care what I think. I adopted a one year old pitbull mix back in March, and he has been amazing. We have settled into a nice routine, and he knows what to expect on a daily basis. He has learned some phrases and words quickly, and he catches on fast. . .as long as it is something he likes. He has eaten cat food right in front of me, then seems surprised when he hears "No." Doesn't seem to care if I am calling him when he sees something he likes better. When left alone, he will chew things he knows are wrong, despite many okay alternatives. It's not a consistent disobedience. Most of the time he listens great! I am always getting compliments on how well behaved he is, and how well he responds. What people don't know, is that it seems to be on his own terms. I think he has been left to himself for his whole life before now. He has had to make his own decisions and think for himself. I think that is a great quality, until it turns into him trusting himself more than me. Any Advice?