MAD ammeter bypass question

That's a misunderstanding.
MAD is a poor attempt to redirect the recharging current.
If you want to know how much current is going through the ammeter and wiring to or from the battery at any time, just look at the ammeter.

Once the car is running power comes from the alternator. Some goes to charge the battery (if it needs it) and the rest goes to whatever electric items are running. This can be anywhere from 5 amps (ignition & field) to around 25 amps (lights, heater, wipers on). If you want to reduce the maximum current the wires, and especially the connections at the firewall will see, then install a headlight relay harness. That's 9-10 amps that will never go through that connector (unless your alternator fails and you're running on battery). The relay harness will also address the increased load on the headlight circuit caused by replacement headlights drawing more amps than the original 6012 lamps.
I did understand that the headlight relay is a great way to reduce the current. Up north here I will rarely need them and I think they will remain stock. However, in a situation where the battery needs charging, then there will be higher current draw as you mention. I've checked out all the connections and the engine harness is new so I probably don't need an ammeter bypass or this shunt but while I am redoing everything why not?