These are great and amazing little frogs. I stumbled upon them quite by accident myself, and I have literally fallen head over heals for these guys and their amazing calls. To answer your questions:
Gut-loading is when you feed crickets high quality food so that when the frogs eat the crickets, they are getting the best possible protein and not just empty calories. For instance, I feed my crickets a variety of fruit and vegetables as well as a bit of cat food 12-24 hours before I feed them to my frogs. I then dust them with calcium powder and my frogs have a great meal on six legs that they can't resist. As for eating that many fruit flies every other day, I wouldn't be surprised if 2 adult Pacific Chorus Frogs could pack that away-these frogs love a good meal, but it seems a bit high for each frog to eat that much. It would definitely be a chubby frog!
I am not sure how long these guys live for. Paul from NW Amphibian Rescue would have a better idea. To guess, I would say approximately 3 years, give or take.