If the actor, as you put it here, is not deep with emotions, then who is.
I’ve always thought that when Rumple told Bae his mother was dead he was lying. He just didn’t want the boy to investigate any further or start looking for her, and by saying so he stopped this conversation. That’s how I interpreted the scene, but I guess we have to wait for writers’ explanation. I don’t think anything so far suggests he killed her though.