I think some people are naturally a lot more fun and loose over text because they can read something a second time before sending it, so they have a chance to make sure it is okay. When I am talking verbally, sometimes I am a little more reserved (especially with a new person) because I don't want things to come out wrong or be misinterpreted. And some people are just shy. If you are okay with that and are still interested in getting to know him then I would say keep going, because it does sound like he is into you. He might loosen up a bit once you guys hang out a little more, and if he doesn't then you can stop when it feels like it's not really worth it.