Please do not raise a dog using a vegetarian plan - you can do serious health damage by feeding dog food from non meat sources exclusively - please read this:
http://www.goldenretrieverforum.com...-retriever-health-anatomy-physiology-breed-standard/455266-low-taurine-dcm.html
You have done this by feeding him people food (I'm not judging, I have a collie who would also rather eat people food so I have some experience.) You are going to have to follow the tough love advice. So, one more time for the cheap seats: Every morning, put one cup of kibble in his bowl. If you wish to add a little warm water to it, that's your business but understand that what you are doing now is what you will be doing for the next 12 years. Give him 10 minutes to eat. Make sure it's not chaotic, give him room. If he doesn't eat, pick it up. NO treats or anything until the next meal. Repeat. If he doesn't eat after 10 minutes, pick it up. No treats AT ALL until the next meal. He will be happy to turn his nose up for a day or two but I guarantee within 3 days he will be finishing that bowl. You really need to nip this in the bud now, keeping him lean is absolutely best for him, he is healthy he will not starve himself. Dogs are generally just fine to miss a couple meals, do not cave in. You can do this