EFI tank with Carbureted engine plumbing questions

Imo you want to use the wrong fuel pressure regulator. The one you linked in you post is for a carbureted application with a low input pressure! There are dedicated FPRs for running carbs with an EFI pump. Directly from the Holley webpage:

"Most fuel pressure regulators are designed to operate either as a dedicated low-pressure device (roughly 3 to 16 psi) or as a high-pressure regulator (40 to 70 psi). Recently Holley has released a billet fuel pressure regulator that can do either job with a range of 4 to 65 psi (PN 12-879 or 12-880). The regulator comes configured as a high volume, low-pressure regulator but can be reconfigured to control high pressure just by changing a spring that is included with the regulator. This is designed for enthusiasts who are currently running a carbureted system that may at some point convert o EFI. This saves the expense of purchasing a separate regulator."

How to Choose a Fuel Pressure Regulator For EFI or Carb