I'd talk to whoever you ordered it from, if you're keeping it they at least owe you a partial refund as it's going to be a less expensive battery than the 1200 CA one.
I'd second (or third, fourth, whatever number we're up to) just sticking with the stock pads for now and upgrading your brake fluid to a high temp DOT 4 one. I'm currently running Motul RBF 600 and didn't experience any brake fade even on a 10 lap session.
Just got back from my first dry track event with the Supra. Was a weekend event at Gingerman Raceway. Had a total blast. It was also my first time at this track. My times improved all weekend. By my last session on Sunday every lap was faster than my fastest lap on Saturday, and day over day...
Looking into doing a lug stud conversion. Is this a good option:
https://speedindustry.com/conversion-stud-14125-to-1415-78mm-black-bullet-nose-stud-kit