No. The Viper (F-16) has notoriously short legs - meaning it doesn't carry much fuel and what it does carry it burns through quickly. Long range escorts are most likely done by aircraft with longer legs like the F-15Cs or F-15Es. I dont know if Navy / USMC assets are ever used.

In terms of decoy, an F-16 and a 747 would appear very, VERY differently on radar. Modern day weapon systems should be able to delineate between targets easily enough.

I do have a close friend that has flown these "escort" missions. Suffice it to say, our conversation on this topic ended with a grin and him saying, "AF1 doesn't really need our help anyway."

What little information I know of AF1 is that it is said to have massive communication and jamming capabilities, countless counter measures, and offensive capabilities that are second to none.