Kenny always needed a slap in S1. Not much has changed. It seems worse because A) he wants to die but doesn't have the balls to take his own life and B) instead of arguing with a grown man like Lee, he's taking his frustrations out on a kid.
Luke sleeping with Jane makes sense. He comes across as the amiable 20-something big bro/good guy, but he's actually a selfish git when he need arises. That much was pretty clear in Ep1 when he was carrying Clem, then dropped her in the mud when he thought she'd been bitten.
If anybody's going to carry the baby, it'll be Christa. She's due for a return and an explanation of what happened to her baby.