I've never dealt with pool chemicals, so this is just an educated guess.

Bleach, i.e. sodium hypochlorite, will rapidly degrade once you dilute it in water. Hypochlorite ions from calcium hypochlorite may or may not degrade as fast when diluted. But if it does, then most of that 2 gallon stock solution may lose its potency before you can use it up.

If you've never used this technique before, I'm really curious about the results, if you could do a test some day. Mix up your stock solution and store it for a couple weeks. Then add it to water according to your directions and see if it satisfies the sniff test. I suspect that even repeated applications may not ultimately pass the sniff test because there aren't enough hypochlorite ions left.

It would be great if it does work, though.