Hello: To start, I think you have the date code right. Often though, you will fine a date code on a new heater that says the heater hasn’t been made yet. Seems an allowance is made for time spent in the distribution system. When looking at your bill are you comparing dollars or KWHs? I’d expect dollars to be way up even with the same usage.
Try turning off everything and checking the rate of meter spin. Then turn on power to the heater, when it is already hot, and see if the meter spins. Normally, if the water heater uses power, it is converted into heat. So, if it isn’t overheating, it isn’t using excess power. A leak to ground could be the exception. Search for “leak to ground” to see what else has been said on how to check an element.
The anode is under that knock-out and it would like to be checked. 😉 If it is used up, a new heater could be the right move, otherwise not.