I would honestly not worry about adding more and more different types of training and just focus on core, foundation things right now.
Impulse control around food (as you are doing) is one.
To be able to take valuable things back off the dog is also important. Do this by swapping them for something else even better. e.g. play with one toy for a bit then hold a bit of suasage near the dog's nose and when he drops the treat for the sausage, praise him and give him the food, then give him back the toy. Over time you can add a cue word (e.g. "thank you" or "drop") to the action. This way he learns that giving up toys is always rewarding. Do the same for chews and bones but only if he seems chilled about it.
Look at me is also great and easy. Sit or stand quietly near thre dog with some treats. Every single time he makes purposeful eye contact with you, say "good" and give him a treat. Over time this builds up a great association between good things and keeping his focus on you.
With the harness, GO SLOW. Many dogs don't mind it but some an be permanently freaked by it. Far better to have a few sessions building up to it. e.g. puppy sniffs harness, you say "good" and give him a treat. Repeat until he looks exited to see the harness. Then maybe progress to bringing it up to his head but no more. Then to slipping it over his head. Then to clipping it up. Then to having a lead attached. It's worth going slow for a lifetime of him loving his harness.
Wait is also a great one. Don't feel bad you've only got 1 second of wait right now . That's entirely fine. Just build it up over several weeks.
Reinforcing being in a bed or on a mat is also useful. Mats especially because you an take them anywhere and have somewhere the dog is happy to settle. Whenever you spot the dog in his bed/on his mat, praise and treat.
Strengthening a rock solid sit is useful. Over time build up to being alble to walk around the dog while he sits, then being able to walk off and return. Once you have this, you will find it easier to apply to different situations like through doors etc.
Working on recall in the house is also great. Have someone gently restrain the dog while you walk away, perhaps to the next room. all him and they release him. When he gets to you be ready to reward with play or treats Do this all over the house and garden and you will have made a great start to outdoor reall.
This stuff takes time. It's frustrating because we humans think we need to see significant progress every training session. But we won't. It's not like that and, in fact, the best learning happens between sessions while the dog's asleep as that's when his long term memories are organised. If you have got all the above by six months old then you're doing well 
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kikopup on YouTube is brilliant, btw.