Stock alternator up to the task? If not, how many Amps will I need?

The alternator provides power for the vehicle while the engine is running. Battery is a storage device. Why do cars run at 13+ volts and you don't see static batteries with more than about 12.7 volts?

The welded factory power splice is between alternator and ammeter, that is the side the power is coming from. The residual is supposed to flow through and keep the battery charged, ammeter intended use.

I see a lot of people, including sellers of electrical items, suggest pulling power from the starter relay. That is a HORRIBLE spot to pull power on most every mopar with OEM wiring. Where you pull power depends on a few factors. In some cases there is no perfect point to pull power.