Diagnosing a drive/start issue with my 2000 4.3V6Chevy Blazer?

I was driving my 2000 Chevy Blazer up a large gradual hill to work this morning when all of a sudden it started losing power and almost sounded like the engine would high-rev to get power enough to pull off to the side of the road. Roadside istance guy never tried to jump the battery (even though the battery indicator light illuminated) but instead insisted that my fuel pump may be going out after hearing it try to start. {Pretty much sounds like if its starved of gas, it's not partial because it dry spins-No chugging-. Cranks quick and hard, but not progressing toward starting, just gradually getting slower until you hear a repetitive, fast click like the battery is dead} SO, he hit the gas tank with a mallet while I tried starting it and it never chugged or tried to do any more than crank. I'm thinking the fuel pump may just be a worse case scenario, but don't know the odds that it may be a clogged filter or blown vacuum line or clogged injector. Any possibility that the symptoms fit a bad ground wire for pump or some kind of alternator/battery combination problem with system power?