Can the calibration fluid be stored and used again?
Probably not, depending on what it is, and what gas (air?) it's exposed to in your fridge. CO2 in the atmosphere dissolves into standing water, and (long story short) lowers its pH. Lower fridge temps will slow, but not stop, this reaction.

Also, the pH reading of a solution is temperature-influenced, normally there's a table of value offsets for solutions that are not at 77 deg F. So, you couldn't use your cal solution right outta the fridge.

Looking at an old bottle of GH 7.0 reference solution I have, it says it CAN be used for a storage solution as well. Never noticed that. It's reading at 1330 ppm, though. I'll probably just use it up as storage solution --I don't really trust calibrating with anything that's not a fresh-opened package. I like those little single-use things, myself.

Just make sure your storage solution has some "TDS" to it. Storage solution needs to have some electrical conductivity to it, at least for the meters I'm familiar with. And some probes like to be stored in an acidic environment.

My tap is 1740 PPM, no thanks.
Texas, 1740 ppm is prolly better than distilled. MAYBE better than RO, depends on what's left in it after processing. That is some crunchy H2O, though. Thought mine was severe (it's about 740). Lemme ask Weezard to check in on this. I don't wanna lead anybody astray. I'm jes' sayin' what I do with my $25 Milwaukee POS pen. I'd hate to have you mess up a precision instrument following my questionable lab techniques!