First of all what breed is your dog?
Secondly i wouldn't worry too much. If he is still active and running around then he is eating enough. You would be surprised how little some dogs eat. I have one Toy Poodle boy (over 1year old) who eats around 20-30 kibble pieces a day. He has more energy than any of my other dogs and is the perfect weight.
Its a really bad idea to force or hand feed your dog as you will teach them that if they don't want to eat, they will get hand fed (think about it this way, would you rather feed yourself or be fed?). If you are worried that he isn't getting enough nutrition, pick up one of the supplement pastes (nutri-cal, nutri-gel, puppy paste etc.) and give him a pea sized blob every day (i do this for my toy dogs until they are 6-8months old anyway.
Also it is not advisable to mix traditional kibble with BARF style diets (Raw dehydrated is basically BARF). I would stick with one or the other.
All in all, just don't panic, he will eat when he needs to. Unless there is something majorly wrong (health wise) a dog will never starve itself given the choice.
sorry, didn't see this bit.
If you have a dog such as a poodle, shih-tzu, maltese or something else with a longer coat that can be clipped into a teddy bear clip, allow your groomer to create the illusion of "cute fatty puppy" with their coat. Making your dog overweight (even just a little bit) for your own aesthetical pleasure is slightly cruel and financially inadvisable (due to the health issues related with obesity in dogs).
A dog that is groomed to look 'pudgy' is always cuter than a dog that is well padded (as long as he is groomed well by a groomer who knows what they are doing.
You can feed your dog cooked food if you wish (although i would make sure he is eating enough kibble first, feeding 'human food' will often make picky dogs even more picky. I would always recommend cooking the food yourself however to ensure you know exactly what is in it and how it was prepared. If you are interested in cooking for your dog (either as a staple diet or as an occasional treat) i can pm you a list of things to avioud as well as a list of things that are actually good for dogs.
Thank you very much for all the information. My boy is a Cavalier King Charles Spaniel puppy (5 month old). As you said its better to let the puppy to eat the food rather than hand feed him. And will get those supplement for him. I think its just me the one who worry too much about his food intake and I never know Addiction Raw Dehydrated is basically BARF food (he love the food so much).
For home cook food, I will still prefer kibbles in the moment as I dun normally cook at home. But I would like to said a million thanks to you for providing me those very useful information about my puppy problem.