How to break out the due power supply and USB connectors?
so 1 - yes. the VIN pin has a common trace with the barrel jack, you can verify with a multimeter in continuity/beep mode. ive actually put power out through the barrel jack on a mega.
2- i cant find a clear schematic for the due at the moment, but on the mega the rx/tx pins are also common with the usb pins, thus they are not usable while plugged into usb