I would understand it as a pre-"I love you". It means he cares a lot about you but doesn't yet want to take the step of saying he loves you.
This is richtig! 'Hab dich lieb' is a milder expression when compared to 'Ich Liebe Dich'. Sometimes (depends on the context), it might mean that someone doesnt really love you, but cares about you. Depending on your position, feelings and how long you both have been together, you can figure out what that means. Einfach!