The pills Gustavo Fring takes are "activated charcoal" tablets that apparently can soak up poison and help delay the actions of it.
Jesse's cook results in a purity of 96.2%, lower than Walter's standard of 99% or more but marginally higher than what Gus was willing to accept from Gale. Remember, too, the poor sanitary condition of the Mexican cartel lab and that ingredients like Phenylacetic Acid had to be synthesized there first. Under these conditions, 96.2% might be considerably better than expected. Don Eladio also points out this is better than the cartel's chemists can produce.
The Safiro Anejo Tequila used to poison the cartel is the same fictional brand featured in BETTER CALL SAUL where the distinctive copper bottle top is coveted as a memento of happy times.
"Salud" means health in Spanish but is also what Mexicans say when toasting. In this context, it means "Cheers!"
20 years before this show, Jonathan Banks (Mike Ehrmantraut) and Steven Bauer (Don Eladio) starred together as an FBI controller and undercover agent, respectively, in the fourth season of Wiseguy (1987).