1) clear coat the final part with an automotive clear (or rattle can clear PU) this should provide any UV protection - dyed fibres may still fade2) That's the holy grail of resins there, the colour will always change a bit
3) don't use polyester resin then! - even epoxy you still need to vent the room but you just can't smell the stuff
4) see your resin supplier, I use Huntsman HY-LY 5052, good pot life and good structural properties but expensive epoxy
5) don't worry about this
6) Best talk to them with your requirements then!