I owe it all to 2 things/people:
1. A kitchen scale. After last time's fiasco, I went out to Target and got an inexpensive kitchen scale (literally for the sole purpose of making pau). I realized that 500 grams of flour was not what my googling converted it to in cups.
2. My pal, David. David is the one who gave me this recipe in the first place and has offered advice as I navigate the really confusing world of pau.
And this time, it worked!