Re: The rescue options?
$450 million was the launch. It was a couple of billion to refurb the shuttles after each flight. This swung on the side of making disposables a lot cheaper - but NASA had no man-rated gear to go on a disposable stack.
One of the more fanciful "rescue" options for shuttle involved siwnging a bar out the side hatch and firing astronauts out the door at about 100-150,000 feet but it was acknowledged as more "wishful thinking" than practical - and in any case could not be used until after the reentry stage.
Other rescue options proposed as far back as dyna-soar days involved inflatable bubbles that astronauts would ride in on over a 2-3 day period (with utterly no control over where they ended up)
Even though it was a horrible kludge from the outset, what really killed Shuttle was the stark reality that disposable rockets are cheaper - paying the russians to use their man-rated kit was a lot cheaper - and a disposable stack cable of sending a shuttle-mass payload (vs a shuttle payload bay sized payload) would have built ISS in a lot less time.
Of course if they hadn't spent 20 years fartarsing about trying to do flights which justified using a machine designed from the outset to be a pickup truck hauling - and far more importantly returning - space station components, then there might have been a ISS a lot earlier.
The russians built Buran to prove they could, from publically available documentation for the shuttle.
The designers realised it was incredibly dangerous as-is and wanted to move the orbiter to the top of the stack, but they were told to leave it as it was so it could be flown in minimum time - but that configuration would never have been man-rated under russian flight rules and was one of the reasons Buran only flew once (Buran's undercarriage could be deployed under computer control. The Shuttle's had to be manually deployed (non-retractable) and that's why it could never fly unmanned)
(The russians were similarly shocked at how dangerous the apollo LEM units were. After losing several people early on they were acutely aware of the level of bad publicity they'd get if they lost anyone on a lunar sortie.)