I'm in Ottawa and hav had a similar experience with the CYA results, but with the same store. I've had them tell me it was zero after I added CYA and wanted to check what my level is, and this year I changed liners and brought to new city water for testing and they said the CYA was 30! I have a Taylor 2005 now and it showed zippo CYA.

I would do your own test, even twice to be sure, and take the pool store with a grain of salt.

On the calcium, can you have too much for a heater and end up with a build-up. I really don't know and hope someone here may help.