Re: The first reusable?
~680 tonnes of hydrogen/oxygen in the main tank
~450 tonnes of solid rocket fuel per SRB
So that's ~1130 tonnes that can't be recycled as it has burnt!
That means that 900 tonnes aren't burnt - so its about a 1/3 that got reused. I seem to remember the bit that didn't was the aux fuel tank...
(why do NASA quote everything in lbs so I have to convert to tonnes?!)
I do agree that the design of the SRBs was suspect - as was shown when one failed. But like much of the early space stuff, it was very much seat of the pants design!