Bernoe and Baxter around that age owned me. They had me figured out to a tee. I started them on EVO kibble. They ate that awhile and got tired of it, then we went to Natures Variety raw. They loved that for awhile then once again they wouldn't eat. Dinner time...they just turned their noses up. All this food I was wasting was costing a fortune. So, I started home cooking. And yes, it is a pain getting it balanced...adding bone meal for the calcium, supplements for this that and the other. I started out with chicken. Cooked 20 pounds at a time and bones it, processed it with the veggies. After awhile they again turned their little noses up at that. So, I switched to beef. Talk about cost....and they actually had the nerve to turn their noses up at that. After that...I put my foot down. I of course had to have some encouragement to not cater to their pickey pallates anymore, but I stopped all the madness, keep kibble down all day (rotate the good ones) and if they are hungry they eat. I still do the homemade chicken and give it to them every now and then and they seem to appreciate the trouble now after not having it.
If your baby likes raw you should try the Natures Variety.
Nature's Variety It comes in many different meats. Beef, chicken, organic chicken, rabbit, and venison. Mine liked the more pungent meats, that being rabbit and venison. Their is nothing wrong with feeding raw. I still have it in the freezer and feed it occasionally, because mine now appreciate it all. Lots of Yorkies have sensitive tummies and switching foods can upset them, but I think mine have lead stomachs. I switch around a lot, but never feed canned. That ruins their insides. Some people have good luck with it, but I never have.
Their are many people on here that can help you get a good diet going, what ever you choose to feed. His weight isn't that bad for 8 mos. He may just not get as big as the breeder predicted. If you choose to feed kibble get him a good one like EVO, Innova, Wellness, Instict...any of the grain frees. And maybe you could entice him to the kibble with the canned like was suggested or even a little chicken broth. You'll get him going, he's just searching for something better... hopefully. Best of luck to both you and your pickey pooch!