A Few Training Questions

So, I'm really pleased with how much Loki has progressed. He hardly ever bites anymore, I can actually play with him without fear of biting (minus the accidental ones) . His only real problem now is jumping. He jumps up at us, and also the kitchen counters often, and as soon as I say "ah ah!" he sits down immediately. So he definitely knows not to do it, but he still actually does it. Am I going about it the wrong way, or is it just that it takes time for him to stop jumping up to begin with?

Another big problem is walking past dogs. And people, but mostly dogs. I can make him sit and stay while a dog walks past and he does it, but when we're actually walking past, it's horrendous with all the pulling. He doesn't know the watch me command yet, we're still working on it (he looks at me when I say "watch" but only for a second or two). But even when I used to hold a treat up, he'd alternate his glances between the treat and the dog, so I don't know. That said, he pulls a lot less when I do hold a treat up, so should I just continue with teaching him the watch me command?

I think you have him good on the basics and just have to keep at it , maybe with the jumping make sure the response is immediate and keep him sitting there for prolonged periods until yuou say ok with a treat involved obviously.
Not mastered the walk past myself with either of ours I'm afraid but when I see the good doggies I notice the owner is constantly talking like a distraction and again high value treats I believe are the key

I think you are on the right track. It just takes some time. If he has a real taste for a certain treat you can try using that

You're doing fine - he's still only 5 months old, so loads of time to get the finer points sorted!

It may well be a work in progress, use a high value treat when trying to get him to walk past another dog without the jumping up routine and use the watch command with the treat. You are certainly on the right track.

I have the same problem with Densil - he ignores some dogs, but other dogs he will jump up and want to go for them - to play I think, not aggressively. My trainer has recommended that until he is fully trained - if the distraction with treat doesn't work, to just turn around and walk in the opposition direction if another dog is coming - even if you have to go a long way round.