1. Check out the BLE component datasheet (on TopDesign, right click on BLE component -> Open Datasheet..) to see all the APIs that component supports. Search for advertisement update. For updating the content in ADV or Scan response packet, use the API CyBle_GapUpdateAdvData() with updated parameters.
2. Are the bootloader and bootloadable sharing the same stack memory? If yes, then you can resuse the same API as said above?
3. I am not sure why anyone would want to stop you fro updating the Scan response packet on the fly. I think what you are trying to do is amenable and no issue should come by using it.