Doubt it, not at that price... Likely fakes...
Yes it's the official ebay store. Has 99.3% positive on 1.3 million feedback.
Just a brand name. I find the quality decent and good prices.
They sell clothing that is out of season and factory seconds, therefore are you sure you didn't buy one that was factory seconds? All T-shirts and shorts that I have purchased from superdry ebay have been pristine without any noticeable issues, but maybe you were just unlucky.