Bubbles have returned on the filter head output, and a clear line installed on the supply side of the filter head is full of fuel with no bubbles, so the leak persists within the filter head.
Since all new o-rings were installed, only a few things remain which might be the cause: water-in-fuel sensor leak, cracked fuel heater, or a crack in the filter head itself.
WIF plug ordered, which will hopefully shore things up.