You are lucky! I've seen 4 pounds of BioGard for $12 back when Costco was selling those 12 pound bags for $3.50! The same amount of BioGard was $36!!!!!!!!

Calcium doesn't soften water--salt does. Calcium is to protect the calcium carbonate in concrete and plaster from leaching out.

Chems you DON'T get at a pool store:
Bleach for chlorine (but LC from a PS MAY be a good deal--depends on price).

Borax for raising pH

Washing Soda for raising pH AND T/A--it's WAY cheaper than the PS stuff--and it's just soda ash, same as theirs.

Baking Soda--Total Alkalinity Raiser is the same stuff.

Muriatic Acid--hardware stores sell it.

The only chemicals you need to get from a pool store are:

CYA--Stabilizer.
Dry Acid (if you are spooked by Muriatic Acid).
Polyquat 60% algaecide

Very few pool stores have ANY drop test kit refills, and even fewer have a proper selection. On-Line is much better.