Just to let you know I tried something similar to this. I used reef flux, 2 capsules for 66 gallons of total water. Much higher than your dose but still way under the recommended 6-12 capsules.
Within 24 hours I noticed it dieing off. 3 days and 80% is gone. Nutrients were rising so I restarted the skimmer and was going to add Cobalt Complete Reef that I got on clearance for a few bucks at the LFS. To reduce nitrates without a water change.
Well I turned off the UV and not the media reactor, so I had carbon and chemipure running the entire time. It was about 3 weeks old but still, I'm sure the chemipure still had life yet in it.
So I might try what
@billyocean suggested, run a micro dose for an extended period of time, while running my other equipment. Maybe 1/2 a capsule or less, to make sure it's totally eradicated.
The only thing I had happen at the time, my xenia melted, but I had just relocated it too, so maybe something else caused it. Everything else looks great even with 50ppm nitrates.