Hi warpedak47! Welcome to Basenotes.
I am not very familiar with ebay, but "also the eBay user had 2000+ pos feedback at like 99.7%, however ebay now says he is no longer a user on eBay, seems suspicious" does indeed sound suspicious. That being said, I am not the most informed/updated about which scents have been counterfeited/faked, but the best way to find out if your bottle is the real deal, is to bring it with you to a reputable mall/retailer which stocks it and do a side by side test of the scent. Note that sometimes manufacturers do change the bottle designs over time, and differences may not be indicative of fake goods. I don't have much knowledge on serial numbers, but I am guessing those can be faked as well? Hopefully someone else has specific/similar experience with your situation, can share his/her thoughts. Hope this helps.