1. 500k. The sentence "The purchase price of a fabricated part is half that of a new component" refers to the sale price of a fabricated component, and should benefit from a future errata to add clarity.
2. You need actual C-Bills. The C-Bill value of equipment you stored, salvaged or cannibalized is only relevant subsequent to an actual sale.
3. No, it is not.
(See also the example on p.179 which does not provide a -1 modifier for Life Support.)