He probably heard through the rumor mill that the site was legit but really had no idea if it was or not. He used you as a guninnea pig, so if you got beat, he wouldn't place an order. As far as not knowing anything about gear or pin sizes, pretty common with people. A lot more people then you think start injecting shit in their bodies with needles and gear they got from some guy at their gym. You are worrying too much.