This sounds very much like Gandalf. He's VERY stubborn, but also very smart. You'll notice the pinch and bark collar in all of his pics because, well, that's Gandalf.
It sounds like your dog and mine might be from the same litter. We heard 40ish lbs and gandalf is now a "thin" 80lbs. He's very loyal, protective of the house, and us. He is much more bonded to my fiancé than to me though. He likes to play with me and shows affection, but when push comes to shove she is his person for sure. He's super protective of her.
If we're in public he keeps tabs on us at all times. If one of us goes to the bathroom he'll put his paw on top of the foot of the other person while crying. He always has to account for both of us. If a stranger goes to pet him he will always look to us for permission and reinforcement that it's ok.
When he was a pup he never needed to be taught how to heel so he was naturally great off leash, but as an adult he looks to fight other dogs so he's hardly off leash anymore unless we're hiking in the middle of nowhere. Plus, he likes to eat and roll in poop like no other.
Overall he's a great dog, but he does have stupid tendencies. Also his bark, like other heelers, is ear piercing and he loves to hear it. He knows how his bark collar works, but if he sees something worth barking at (like a cat or god forbid a bicycle goes by) he will bark and get shocked... repeatedly. It's not because he's dumb, it's because he wanted to bark and that's that. You need to be very firm with this breed, but eventually they do listen. I will admit that his training was much more "hand's on" than any other breed I've ever had. He's just that pig headed. We do love him to death though.