Source and Destination Packets on Wireshark Relative or Absolute

If you want to inspect and analyse ESP traffic directly your version of Wireshark needs to be linked with libcrypt. More details here.

The destination address is the destination system, Computer B's MAC address.

The traffic's going to go through the access point because the client is associated to it (which is a different field in the 802.11 header, the recipient); the destination isn't the access point unless the access point is actually the final destination for the traffic on the layer two network - for instance, accessing its management interface or, if it's a router, sending traffic outside of the subnet.

802.11 was designed to work on many of the same principles of 802.11, which is why these access points can work just fine on the same layer 2 network as ethernet; just think of them like a switch with invisible cables to each associated client.

Yes, the frames need to be format-munged at each hop when changing media, but the headers always contain Computer B's MAC as the destination. Access Point 1 keeps track of the fact that Computer A's MAC address belongs to an associated client, while Computer B's MAC address is out whichever ethernet interface that Access Point 2 is plugged into.

Every switch or access point in the layer 2 network keeps track of what MAC addresses are accessible via a given interface, which is what allows each device handling a frame to independently make a decision about which interface to send it out of, be it wired or wireless.