As for the shrimp being safe, they are at least safer than feeder fish because they can't carry many fish diseases (parasites can be an issue, just don't buy them if there are dead shrimp in the tank at the LFS and keep an eye on them when you quarantine them and gut load them) and they don't have thiaminase like goldfish (an amino acid, I think, that blocks absorption of thiamine, which is necessary for the fish's health). I gut load mine on high quality flake food containing vegetable matter, algae wafers, and some calcium enriched crustacean food. The crustacean food is more for the shrimps health in my case, because I keep my freshwater tank stocked with them to save trips, keep an eye on them, and get them healthy and gut loaded because I feed them fairly often to my puffers. It's a good way to get vegetable nutrients to them and it gives them some entertainment once a week or so. Essentially gut loading is a good way to get whatever foods and nutrients you want to your fish while still giving them fun to chase live food. Most live foods are lacking in nutrients on their own in comparison to commercial foods. It is also a more natural way to give predators a balanced diet. Carnivores get most of their vegetable nutrients from the stomach contents of their prey in a form they can digest better. That's how the food chain works.
Garlic is really really tasty to most fish. It simply makes food more attractive to them and seems to stimulate appetite even in picky fish. You can buy commercially made garlic solutions in most LFS's, if you can't find it with the freshwater stuff check the marine section. It is used very commonly in saltwater aquaria to entice wild caught fish to take frozen or freeze dried food. If you can't find it or just want to give it a try before buying a bottle (in my LFS it runs about $8-10), just mince some fresh garlic cloves finely, mix it into a small cup of tank water, and soak the food you want to offer in it for 10-20 minutes. I would do this with a frozen food that has pieces big enough to pick up and feed individually. Then pick out a few pieces and offer it to the fish. I would recommend bloodworms or perhaps beef heart. Both are rich meaty food that the fish should be happy with even without the garlic. Try not to feed too much beef heart, it is very rich and kind of fatty, which isn't good for the fishie liver, and an unnatural food source for fish. Cows are usually not on the menu underwater... As for feeding frozen food, with or without the garlic, always defrost in a cup of tank water before feeding! Eating food that is still frozen can lead to lethal temperature shock for your fish.
And lol at him making sure you can see him. That's what they do. I wouldn't be all that surprised if he is swimming around when you aren't in the room like everything is fine...
give him a few more days and maybe try a treat like bloodworms to entice him out if his hiding spot.
