320 ppm is high but it's not arsenic, plenty of people pull great shots with hard water and just descale on a schedule. The real question is whether you actually tested the water before or after you bought all that gear, because it sounds like you changed five things at once and are giving all the credit to the filter. Maybe the grinder and beans were fine and you just finally dialed in your recipe the same week you got the filter. Plenty of us have blamed water when the truth was stale beans or a grind setting that was off by two clicks the whole time.

A spare standoff shorting the board got me too, cost me a whole Saturday.

Fifteen minutes on the phone can flip everything, glad it worked out for you.