I'd continue with the Corid, but with that much blood, I would get a sulfa drug like SMZ-TMP or use Toltrazuril to treat the Coccidiosis.
For the worst chicks, I would direct drench them with undiluted Corid at a rate of 0.10ml per pound of weight for 3 days. This is in addition to you syringing the mixed Corid water into them as much as you can throughout the day to keep them hydrated.
I'm sorry that you lost one, you have looked at vents to make sure there's no injury or vent picking right?
Not sure what's going with the funny sounds, if you have video that would be good. Upload video to youtube and provide a link. Your adults may have respiratory illness that is going through the flock, hard to know. I'd look inside beaks for lesions to be sure it's not something like canker.
Coccidia is species specific, so the strains of Coccidia that cause infection (Coccidiosis) in poultry are not the same strains that would infect your dog.