When driving along parked vehicles, how far away should you be from any parked vehicle?

There is no law or rule that answers your question.
Generally speaking, you have to stay far enough away from the cars so as not to hit them
with your car. You also must stay on your side of the road, you can't cross the middle
line of the road just because you are driving along parked cars. Safe driving practices
would dictate that when you are driving in this situation you should slow your vehicle
down to a safe speed. There is always the possibility of course that someone may open
the door of one of the parked cars to exit. You should be prepared for this and be able
to stop your vehicle quickly if the need arises.