Unless you have a fuel pressure gauge you can hook up to verify function?
Otherwise the tough thing is that you won't know until you actually pull out the fuel pump. The hardest part is all the maneuvers to get the pump out. Once you're there, might as well just replace/rebuild it. Both options available through our esteemed member Barrett.
I have an '07 XB9, and it turned out that there was a pinpoint hole in the flex hose component of the fuel pump. The pump would turn on and make all the right noises, but with that hole it wouldn't pressurize the fuel properly.
Or wiser head will chime in with diagnostic advice. Looks like you chased down all other likely leads though. Except maybe pull the spark plugs to make sure they're not ruined? And visually confirm spark?