grab another set of test kits imo, salifert should be good. it's a small cost, but it will give you more comfort that your RS test kits are reading well.
how are you measuring your salinity? a refractometer? or a hydrometer? large temperature difference between your salt mix water and your tank water could have an impact on your readings.
http://reefkeeping.com/issues/2006-12/rhf/index.php
anyways, your parameters are very unlikely to be the cause of fish death though, although the 100ml 2 part dosing with a low coral load seems really suspect. i've got a reefer 525 with a medium high coral load (100+ lps, sps frags/colonies) and i am only dosing 60ml a day.
if it were me, i'd stop water changes until i get another set of test kits to double confirm. also toss in an ammonia test kit just to rule ammonia out too.