I don't know about raw shrimp, I'd really only use it as a treat. Feeder guppies can be good but it is usually recommended to quarantine them for 30 days before offering them. I would try to get some blackworms or bloodworms for your little guy.
Once they are morphed they will love feeder roaches, mine do. My smaller tiger is also a bit particular about her food size, she much prefer to be fed a worm cut in half. My big tiger seems to gobble anything I offer.