You mentioned you are waiting for your new battery to arrive, when it shows up, fully charge it prior to installing, especially if it comes "dry", add the acid, let it sit, bounce it around a bit every 10 minutes, for about a half hour, then place it on charge (2 amp) manually and make sure it comes up to 14v...
(tenders are not reliable "chargers", like a manual charger... a tender will sense a charge, and say it's charged, when in fact it takes a deeper "cycle" to really charge the batt, and return the electrolyte to usable...and if there are mini shorts, or any sulfation/debris in the batt, you never know it.)...then proceed from there.
I'm thinking even tho you been charging and messing with the battery you have, it's toast internally, and if "load tested", it would show as "bad", even tho it shows 12+ volts, without a load, you can't bet its "good"... if you are only "checking" volts.
don't freak out further, and rip a whole bunch of stuff apart, like the dash, and ignition switch, and anything else, until you get your new battery done, and installed. Creating a grocery list of stuff removed and messed with just makes it more difficult to analyze the issue.