Given a conversation is occurring using HTTPS, during the handshake, can the man in the middle interpret all communication from the server to the client?
Assuming that the man in the middle can receive the packet, and open it (using the public key), could it then pass the unmodified (encrypted) packet which it received from the server? It would receive back a packet encrypted using the public key (which it would not be able to interpret), but would this allow the man in the middle to eavesdrop half the conversation?
Assuming that the man in the middle can receive the parcel, and open it (using the public key), could it then pass the unmodified (encrypted) parcel which it received from the server?
Yes, the attacker can do that, that's why private key is never used to encrypt data. Public key is used to 1) cryptographically sign data, and 2) decrypt data sent via the corresponding public key. Vice versa, the public key is used to 1) authenticate (verify) signed data and, 2) to encrypt data to the holder of the corresponding private key.