Oof, that can be a hard one. Some puppies are very bitey and pesky, especially until their baby teeth fall out and their adult teeth grow in. Didn't you say you got Harvey as a slightly older but still young dog? Maybe you weren't expecting the energy of a younger puppy. Our first lab, Chase, who we got as a 9 week old, was very energetic and bitey. I had clothes with holes ripped in them from him biting, racing past us and catching our clothes in his teeth, jumping at us and on us. He was an "only child" at the time and his attention was fully turned on us. He was an only child until he was 6 years old and he grew into a lovely, calm, and mostly well mannered dog. We did have to work on getting him not to jump on people and not to drag us along on walks, but you have to do that with most dogs.
Our second lab, Lark, we got at about 11 weeks of age, when Chase was 6. I was initially so pleased that she was so much less bitey until I realized she was focusing all her biting on Chase. The poor boy had scabs on the scruff of his neck from her vampiring him and tormenting him non-stop. He would never, never correct her. We spent a lot of time trying to redirect her energies onto us or onto toys. I tried to always have something else she could bite or carry in her mouth. The biting seemed to lessen as she got a little older, meaning in months, not years. But we did feel like we needed to protect Chase from her for a few months and we found nothing we did would get him to correct her pestering behavior.
With our younger boy, Henry, we had the opposite problem. We got him when he was 9 weeks old and Lark was 6. She was all about correcting him, without him even doing anything that we could see to provoke her. We had to protect him for several weeks through close supervision and never leaving them alone together until he got some size on him and she seemed less annoyed by him breathing the same air as her. He really didn't seem as pesky a puppy as either Chase or Lark had been but maybe that's because we were being so careful with them being together. He's always been exceptionally well-mannered.
So, young lab puppies can be very pestery and bitey. They are energetic and can make you want to pull your hair out. I think you will have to continue to redirect Johnnie's energies when he gets too obnoxious for a while. Try to have something else you can stick in his mouth if he's biting too much. Sometimes they can get more wild if they are overtired. If he hasn't had some rest time recently, you could put him in his crate for a little bit to rest and reset, like a baby taking an afternoon nap. While Johnnie is resting, you can spend some time with Harvey. He can come along with you whatever you're doing for example, so he knows he's still your special boy and that little interloper, who is taking so much of your attention, is not more important than he is. Include some short training sessions throughout the day, such as getting Johnnie to come to you when you call him, learning to sit, down, and "leave it" as well as one-on-one play sessions. You want him to start thinking you're the most intriguing thing around. When my puppies are 5-6 months old and have had most of their shots, I take them to group obedience classes.
Good luck. I'm only making suggestions based on what I've tried, not on any special secret knowledge. Hopefully some others can offer their insight as well.