If you were on 4.1.2 firmware, the 4.3 image in the op should work. Its been proven before.
Yes. Remake the sdcard. Can't recall if its in this forums op, but I personally used and prefer the Linux method of creating the sdcard. If its not here, go to the thread in the development section in T-Mobiles S3 forums. Its stickied at the top so you can't miss it. It has instructions for using both windows and a Linux LiveCD. Just don't use any Debrick.imgs from there.
As for the card itself, I hope things have gotten better about it, but in the past, faked sdcards have come from places like Walmart, best buy, radio shack, etc. The only way to truly know before buying is to make sure they are an authorized retailer. This means they buy direct from the manufacturer. Otherwise there could be multiple parties between the two which is where the problems occur. If you want to know more about it, there's tons of info and advice all over the net about this stuff. There are tools you can use to determine yours is the real deal, or a cheap knock off too. I can't remember what they are or what you have to look for when using them, but the info is out there.
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