Using cal-hypo in a vinyl pool makes very little sense. Your calcium level at 50 was just fine; at 240 it's total overkill (those poor birds, waste of a stone ) You could easily wind up with calcium scale along the water line and, worse, cloudy water and that could be a bear to get rid of.

It's curious that your CYA is dropping. If I remember correctly you had tested it at 50 ppm at one time. Do you have a lot of splash-out which requires refilling? That might account for the dilution. Or maybe your testing procedures are getting better.

I completely sympathize with the longish drive to the pool store. The Leslie's nearest to me is about 30 minutes away. They do carry Taylor reagents and I've bought refills there in a pinch. For the most part I stock up by shopping online at Amato Industries. There are, of course, many other online sources for Taylor refills.

You can work "blind" for a few days, especially since your pH looks good. Be aware though that the accuracy of pH measurements decreases at FC concentrations above 10 ppm.

According to the Pool Calculator you need to add 160 oz of 5.25% bleach to raise the FC from 15 to 20 or from 10 to 15. That 1/2 gallon you poured in will keep chlorine in the water but not at the levels needed to knock out the CC you're fighting.

Stock up on your DPD and FAS test reagents and make it a point not to run out again. Oh, and stock up on bleach and never mind the cal-hypo. We want to get you swimming in a clear, clean and sparkling pool, not be out there killing birds