[LX5liter]

"I thought a fuel pump either worked or didn't work."

Fuel pumps can get weak. I had a vehicle ( Ford van ) that would idle and start fine, and drive decently when cold, but after about 5 minutes of driving it would buck and hesitate something awful. I could switch to the other tank and it would run fine. I put a new pump in the tank and it solved all the problems.

"Sometimes when I drive my '88 and I "floor it" it seems to act as if it's not quite getting enough fuel and then it picks up again in a second or two. Could that be a sign of the fuel pump going bad?
It's the original pump with 80K miles. Is that about the average life span of an electric fuel pump?"

Fuel pumps should last longer than 80,000k but that isn't to bad of a life. Running them out of fuel will really shorten the life of them as well.
Have you replaced your fuel filter recently?