Hi Marc,
Let me answer questions #4 to #5 and move the post to the Non-Isolated DC-DC so that the TPS4K team can help with answers #1 to #3:
4) If your Vin is just around 9V and won't exceed the 14V max, then yes, just tie the VCC pin to VIN.
5) When you operate at lighter loads then you will have the Discontinuous Conduction Mode (DCM) due to the inductor current hitting the zero Amp threshold. This inductor will not be allowed to go negative by the external Schottky Diode, so it'll become discontinuous in nature. In this state you'll have a Ton, Toff and Tidle, so the measured switching frequency will be lower than when it operates in CCM.
Best Regards,
-Juan