Give him a couple of hard twitches from time to time (hopefully you've got him hooked good)...and be PATIENT!!! The twitches will open the wound more and add to the injury, force more blood/scent out of the wound and slow him down. When the school of baitfish is that much larger than the school of predators, the predator is much more selective. Also with a smaller school of predators there's much less competition so they take their t-i-m-e, you said they were " picking them off "...not blitzing right?
....be patient.
You said you had to "make a big cast"....so there's definately NO chance of re-rigging/hooking and casting him back out to the school to live-line. If you really want to re-rig, cut yourself off a sweet piece-a-bunka >>6oz (?), whatever you can get the most distance with (no lead to counter the cast), fresh bunker WILL sink and be PATIENT.