Well, in the Fullmoon quest, choosing to go after Logan instead of Bernard during the werewolf incident in Bareshade at night will earn you a heart.
The 2nd heart I think comes from a combination of a lot of events. I think the reqs for the 2nd heart are: Working out with him, Clashing with Barrel at the bar, I don't know if finishing the Fullmoon event is also required but might as well try, completing all the Bareshade Expansion, and then finally inviting him to the Fair to watch fireworks.
Take note that this is exclusively on a Discouraged/Normal Logan route. But I'm guessing you have the normal one since you've reached 60 likes on him, which I find impossible to do on the Encouraged route.