Mac Taylor while visiting his dad in the flashback wears the rank insignia of a US Marine Corps Major. In Charge of This Post (2006), his USMC rank on a separation document was shown as Sergeant, meaning he never rose above that rank before leaving the Marines.
The doctor with the peanut allergy shows up to a restaurant and requests no peanut dressing on his salad due to an allergy. The Grave Digger hacks the restaurant system and changes the order to make sure he eats peanut dressing. He ends up on life support after nearly suffocating. Surely a doctor with a nut allergy have an epinephrine pen on hand.
After saving Gail Kim from the elevator and then getting out before the elevator fell with doors closing, the next shot shows Mac getting back to his feet and you can briefly see the elevator car was still on the hospital floor with the doors wide open.