Fuel pressure dropping while driving and under acceleration to zero at idle runs 4 lb electric Blue

I can't tell for sure but it looks like the pump is mounted AHEAD of the axle. And you essentially replaced the fuel line from going up and over the axle to now coming straight from the tank, under the axle, and into the pump. If you've already plumbed it, I'd give it a try.
If it still has issues, make sure you minimize any restrictions ahead of the pump - be it fittings, filters, or whatever. If all that fails, then I'd move the pump behind the axle on the rail for a very short shot right into it out of the tank.