I've never seen that high in Instant Ocean. Reef Crystals usually mixes higher (but not that high), so I assumed that was what you used.
I really doubt your make-up water is to blame. Almost no one has well water that high, and even if you did, and you had a bad RO, and a bad TDS meter, it is high enough you could taste it.
My Salifert Alk kit is slightly high (10-20% at most). If the Hanna checker agrees, I'd assume the salt is off.
You have bad salt. You can risk your livestock and use it, or you can eat the cost and toss it.
Have you tried calling either Instant Ocean or whoever you bought it from? Different companies have different levels of service, but if it were me, I'd at least try for a sympathetic box of salt.