it's indicated that Jesus died on preparation day. So the last supper wouldn't be involved directly with that. I don't think the knife had anything to do with lambs.
The commotion is generally agreed upon to be in response to the betrayal comment, not about body and blood. I believe we have Leonardo's own notes on this. We also have his studies with the apostles identified by name.
The entire scene shown by Leonardo da Vinci is made up. People back then didn't sit at a table, never mind all at one long one, all on one side. They sat on the floor on cushions. This was a staged scene so it looked out over a 'cafeteria' in essence, so the people in the room could feel like they were eating with their holy kin.