If by "kill switch" you are referring to the "tip-over" switch - then I also concur that it would be very much worth checking - especially considering all the items he has already marked off the list.
Back in 2000, my Busa would do the same as you are describing, but I would get about 20 minutes or so out of it if bike was cold/had been sitting initially.
Not so long at all if warm or recently ridden.
Battery would get drained to nothing trying to restart - it would restart and run (a long blurb really) if persistently cranked over, then promptly sputter and die.
I went through the same song and dance as you have - fuel filters/screens, checking fuel pump, fuel hoses, connections etc.
Anyway - long story short - it was the tip over sensor.
Sensor was plugged in and looked "fine" but I unplugged it anyway and sprayed the connectors with contact cleaner.
After that, I never had the problem again.