I think he knows that he's not anybody's dream date, but I think he most likely thinks that's because EVERYONE ELSE IS STUPID.

This I'm less certain about. It may be a question of interpretation. I don't think Snape really cares how he looks (visually) to others so long as they acknowledge that he's smarter than they ever could be. He cares about looking stupid, not about looking ugly. I agree that he uses his appearance to advantage, but I don't think that his physical appearance itself is ever the focus of his attention; I doubt, too, that he has much respect for people who would judge him by his appearance rather than his intelligence.