I don't know if you will need the pump, but your plumming has got me baffled!!!. In picture 1 post #1 your muffler pressure line is connected to a low pressure area of the muffler. I would expect to see a smoke line here not a pressure line. In your second set of pictures you have the low pressure nipple connected to a high pressure nipple (the new one you have tapped), why?
If you connect your pressure line from the 'new nipple' to your tank - top line shown in post #1 picture 3.
Use line 2 (centre line) to fill the tank - then cap.
Use line 3 (bottom line) for fuel to carb.
I maybe 'off base' here but thats just the way I see it .