great so you have the manual.
on propane tanks (I have seen) to close the valve you turn clockwise...it can be hard to see the marks, I highlighted the marks on ours with white grease pencil ( china marker).
there will be slight residual pressure in the gas lines between the tank and the appliances any flame should sputter out.
if not and the flame stays on for more than a few minutes, then we can guess your valve needs servicing.
AND you should have a gas detector in your van to keep you alive- if there is a detector, get it tested.
Mike