My friends had recently gotten a puppy and were having trouble (this was their first time owning a pet). They asked me to embed with them and figure out what they could do to improve sapien-canine relations.

read more
* I think you should give him a treat every time he comes back from a pee. We've found this really reinforces to Cosmo that he gets a treat for going outside to pee. Overall though, it seems like his potty training is going very well so far, so just keep doing what you're doing for the most part. 
* I would try putting him on a shorter leash, especially when he's being difficult and pulling or in a mood where he tries to eat everything off the ground. It'll be much easier to control him and he'll be less successful in his naughtiness. 
* When you're walking him and he is pulling to stop or go a certain way especially hard, try stopping and just standing. I've found that he sits for 10-15 seconds and looks around, then I tell him "let's go" and he'll start walking again with minimal pulling. It can be very difficult to walk him when he's pulling very hard for like half a block, so I had to adopt this approach to get him to keep moving. Often Cosmo will do the same thing, pull especially hard at a certain point. It's usually because he just really wants to pee on a certain tree or smell a certain bush. You don't have to let them do it all the time, but at certain times you just gotta let them have a win.
* When he pees, poops, or does anything else you are pleased with I would say "good boyyyyy" and give him a treat if you have one. Eventually he'll consider the "good boyyyy" to be a reward in and of itself, which can be helpful for further training. 
* I would recommend more "good pets". He seems to calm down/lie down when you're petting him, and he's not very fussy about it. So you could pet him with one hand while reading something on your computer or talking on the phone. Ear and tummy scratches seem to work well. Sometimes dogs just straight up want your attention. I wouldn't be surprised if that's why he starts play-biting you: he wants you to be engaged with him. Maybe you'll only need to give him five minutes, but in those cases you should try giving him a hug, scratching his head and making eye contact as much as you can (he often looks away) and talking to him. Especially with how young he is, I think he needs that attention at times. 
* Try to minimize speaking down about him to each other or calling him names, I think the creation of an "us" vs "this dog" mentality will make it harder to cope with the amount of time, effort, and energy you're going to have to sink into him. 
* Try to take it easy on the research. I think over-researching and being overly careful about day-to-day things will add to the stress of having him. You should be cautious about things that you're making a long habit of, like say you can give him a food that's not great for him for a month but don't do it for 2 years without researching it or whatever, but not every behavior needs to be analyzed and researched. The more little things you have in your head about the "right" way something should be done, the more stressed you're going to feel because it's going to seem like a lot is going wrong. Just sweat the big stuff: potty training, not barking a bunch in the house, not biting and injuring you, not jumping on the table or people. 
* I think it's great you have a schedule, and the music and all that, but I don't think you need to be worried about sticking with it or otherwise he'll turn into a monster. I think certain routines are very important: eating at around the same time every day (expect a justified bark or whine if this doesn't happen), taking him out at around the same time every day (for Cosmo I do 3-4 times a day, usually first thing after I wake up, middle of the day, and sometimes 7/8pm and then right before I go to bed. The older he gets, the longer you should be able to deviate. 
* When you see him starting to bite stuff, try to find him a toy that satisfies him. I saw him biting some hard things and so I got is green bone that smells like chicken and stuffed it in his mouth and yanked it around and he immediately was interested (for a good 2-3 minutes) in biting the bone instead of biting on furniture. When he was done with the toy he didn't continue biting furniture, which is good. 
* Remember: he definitely seems like a normal dog, especially for a 6 month old puppy who is going to have a lot of energy. I'd say he's average or maybe above average in terms of how much of a nuisance he is. You've made great strides so far and I have little doubt it'll be even better in 1 week's time.