Hoover: You are correct about he first class medical now. That was a fairly recent change if you remember, most widebody captains at FedEx have been here a while. If YOUR first class medical is valid, you are good to go.
It has been hashed over on here many times but I will repeat. The FAA may recognize your FEX written past 2 years if you are continuously employed by a 121 carrier, but FedEx DOES NOT.
FedEx is hiring you, so you would want to meet their requirements, not quibble over a FAA allowance.