@Stuntmanmike1977:
IMHO, I would definitely
not put a new fuel pump in now. I've seen absolutely no evidence that you need one. Solve the fuel-filling problem first, then go from there.
Given that (IIUC) you've manually vented the tank by disconnecting the
hose that goes between the EVAP system
vent valve and the fuel tank and you're
still having problems with fuel not going into the tank, it seems to me that the most likely source of that issue (ignoring any other EVAP system issues for the moment) is a problematic "rollover" valve (a.k.a. "fuel check valve" or "fuel inlet valve"). If that valve isn't open far enough, it would explain your immediate issue. In fact,
@Mooseman (in
post #75) and
@Aroc (in
post #139) have already pointed you in that very direction, but I don't see that you've ever fully addressed that possibility. Or if you did, I didn't understand you (e.g. "The original valve is free, just won't go in." -- I'm not sure what that means, frankly).
I've looked at various sources of information about the fuel system on a 2003 TrailBlazer. IIUC, the fuel check valve can only be replaced by dropping the tank, so if you're going to drop the tank, you should probably be prepared to inspect and to test (and maybe even to replace) that fuel check valve.