I don't know how much like you need with Caleb, but you'll need to have at least finished getting the Bareshade Fair going. You need to purchase a heart-shaped cookie from Harold's wife to give to Caleb to get his first heart.
Yes, you can get Bernard's 4 hearts if you choose Logan in the Full Moon event. Considering you can only get any hearts with Logan if you choose him during the Full Moon quest, it's highly recommended that you do so (unless Logan has already been corrupted, in which case it's moot).