Perhaps you got a bad fuel pump? Plenty of parts are bad out of the box especially if they are auto parts store junk. Even good brand name stuff (ACDelco, Delphi, etc) can be defective. Recently I had a reman ACDelco gearbox that was completely messed up.
This doesn't explain why you have good fuel pressure at the engine (it sounds like you confirmed you did) but if the problem went from bad to worse when you put in the new fuel pump I would try to put the old one back in and see what happens. Otherwise, yes, it sounds like from your troubleshooting the spider assembly is a potential problem, but I don't have enough experience to actually be any help in this regard.
What I will say? If you want people to help you stop bashing GM on a GM-oriented forum. I don't mean that in a rude way, but yes, there are a few common problems with these trucks especially the 96s+ with intake gaskets, fuel injection spiders, and fuel pumps, but if you fix that there are plenty of people who have never had one leave you stranded on the side of the highway even with crazy high mileage like 500K+ and even one million miles.