Re:Major Plotholes ... Spoiler Alert (Score 1)

Your second plothole isn't a plothole at all. Joker was taunting them, "I was here, clearly I couldn't have done this" while making it plain that he was responsible/involved. His "What time is it?" comment is followed by something about depending on the time they would be in one place or several. It's a very clear threat that they are in danger and time is sensitive. I think you are reading more into that scene then is actually there.