It's not like they're going to go to waste. By the time he eats through a bag of carnisticks he'll be eating pellets so aggressively you could feed these to him.
As for the tarpon deal, unfortunately thats the way it goes with these guys. Mine was a swimming punching bag for my goliath, but after the goliath got a bit bigger he left him alone. These things are mean as hell ime when they're little. If the barbs continue to be a problem, just take them back to the store. Tell them the truth, they're biting the heck out of a very expensive fish they're being kept with. Get your money back. Then, when you get your next ATF buy three more and keep them until the tiger is eating pellets and repeat. My LFS already knows and understands what I'm doing and I don't even get wierd looks anymore lol. If your barbs eventually settle down, they do make great dithers though.
FWIW, if it makes you feel better, my barbs are fighting with my tigers constantly as well. It doesn't bother me though, I personally think of it as a price we pay to get these guys eating pellets. To me, the cost is worth the results.