When you say you tried testing yesterday afternoon with the K2006 but quit, did the test solution turn pink when you added the DPD powder? And do you remember at which point you stopped counting drops and quit? The 4 gallons of bleach would have added 18 ppm chlorine. You do not need to use any more than one dipper. If there's chlorine, the solution will turn pink with one dipper of powder–unless you have a huge amount of chlorine and that doesn't seem to be the case.

I would add stabilizer just as soon as you can get it in there, using the goal set by the manufacturer of your SWCG. I would start out with some of the liquid product since it's already dissolved and can start acting right away. Expensive stuff though. Then continue with granular until you've reached your target.

Add 2 gallons of bleach every night to stay ahead of what likely is a beginning algae bloom until you have at least 30 ppm of CYA. That would take 72 oz of liquid or 28 oz of granular. This amount of bleach nightly should provide about 9 ppm and keep things under control until the CYA is in.

Raise your pH a little. Shooting for 7.5 you would add 25 oz of borax (20 Mule Team) or 12 oz of washing soda.

I don't know the calcium requirements for a gunite pool and can't offer an opinion on whether your 50 ppm are enough.