It doesn't have to be real-time, but we can leave messages for each other and talk through it. This way we aren't trying to do a back and forth chat in the comments section of your post, which isn't what the comments are meant for.

Re-reading your post, I see this: The switches keep a table of which IP addresses are reachable through each port Which isn't correct, a switch keeps a table of which MAC addresses are reachable through each port. The switch then uses the MAC address to determine whether it should Forward or Flood traffic.

Exemplified in this animation taken from this article.

Reading through the rest, I think it might be best if you sketched out your network, that would help us determine what is happening.

Yes, I think that's a mistake… both layer’s headers use mac addresses, but I need to reread the article. The mac address of an external machine is not known yet.