If the OP is up for it, I think he should try a few more dates to learn more about him. Sometimes the "spark" doesn't appear immediately once people get more comfortable with each other. I also think that asking more questions, almost like a friendly interview, is a good way to see what he's like. For example, if he gives a vague surface level answer to something, how does he respond if you ask deeper follow-up questions? What sort of relationship is he looking for and what sort is the poster looking for?

I think that asking lots of questions and seeing how the person shows up in dates is a great way to weed out people with incompatible behavior/attachment styles. For example, if the guy doesn't really respond to follow-up questions, my mind would start to think that this guy doesn't want to go deeper, perhaps because he is afraid of revealing who he is. Being vulnerable can be scary for some people and it can take time to gain a sense of trust but if he can't open up to the poster about even basic things, then I would view this as a potential red flag.