Hello and welcome to the forum,
I would recommend that you don't feed him any human food. Firstly the lack of consistency may not be helping his digestive issues at all and secondly, it sounds like he is already worked out that if he leaves his food, something better (in his eyes) will appear. I don't have a fussy eater but I think the general advice is to leave his food down for about 20 minutes. If it isn't eaten, take it away and wait until the next meal. Don't feed anything else in between then try again at the next meal time. I am guessing he will eat when hungry but you need to stay strong and not be tempted to feed him in between his meal times or keep trying different foods to encourage him.
You can find some general advice about feeding puppies here
Does he like the wet food on its own as it is complete food and would be fine to feed without the dry food. There is quite a bit of information on The hills Science diet on the forum and it only scores an average rating. I would consider stopping that. Ideally any new food should be introduced gradually but that might be hard if your pup won't eat his regular food. The first link I added also explains the best way to change foods.
There is so much choice and if you want any information about a particular food, hopefully some members may have had some experiences to share. Also there are lots of threads about various foods to browse through.
There are so many variables and each dog is different. Most have us have just settled on a food that suits through trial and error.
You can also look at this thread
to see how to search for a suitable food. It should give you some ideas. I hope this helps. Good Luck.