I always saw Dex as someone who wouldn't care about gender. Demisexual would be my headcanon for his sexuality.
Though I do have headcanons for how he would react to having a boyfriend.
If you were secretly in a relationship?
He wouldn't mind, since he doesn't really have anyone he would tell anyway
He would talk about how you were all his and he didn't have to share your attention
He would follow you and watch you from a distance just to make sure you didn't tell anyone about him or flirt
If the two of you were openly in a relationship?
He would go everywhere with you
He would look off-putting on purpose so people wouldn't approach you. (It would be easy, as he puts a lot of effort into making himself look approachable and friendly)
If he trusts the other person though? He will not stop talking about you. To a creepy extent. People would ask if you are safe. But you love it.
Everyone would assume he tops (he might, but he definitely doesn't Dom that's for sure)
