Personally, I would suggest you take the oscar back or move him to a larger tank if you have one. You need at least a 50 gallon for an oscar, if not larger. Eventually, he won't even be able to turn around comfortably in a 29g. Also, while he is definitely still a baby, you really risk killing him by stunting his growth in the very near future. Oscars grow fairly quickly in a proper environment. By placing him in a tank smaller then required, eventually his exterior will stop growing while his internal organs continue to grow, forcing him into a slow and agonizing death.
(Hate to sound harsh, but these are the facts).
As far as feeding goes, you could try feeding the barbs at one end of the tank while you feed the Oscar with a turkey baster at the other end of the tank, using the baster to drop the food literally right in front of him. (this is a common way to feed Discus).