Yes, fuel pumps can fail over time. That is one of the reasons electrical diagnosis is so tough. Components may work fine for a while then intermittently fail or degrade over time. The pressure could have dropped and it only takes a few PSI in either direction to make the engine have problems.
Finding a vacuum leak can be really tough. I use a thread or a string and hold it near areas where parts are bolted together wherever vacuum may be present. If there is a leak, even though you might not hear it, the thread will get sucked towards it. It has worked for me and I found a leak I looked for for a while at the area where the throttle body meets the plenum. It works very well.
I hope things go well and don't hesitate to ask more questions if you have any.
Take care.
Saturday, August 17th, 2013 AT 12:56 PM