Good plan, but that can be done just as well when he's 6 feet from you also. I like the idea of telling him don't approach from further distances, but that usually doesn't stop them from continuing on their path to intercept. You could be telling him that from 20 yrds to 6 feet just as easily.I've already failed if he's within 6 feet of me. I'm going to verbally intercept him LONG before that in this scenario. I will make it VERY clear and in no uncertain terms that he is NOT to approach me. I won't be waiting until he's 6 feet away.
I'm talking about opening a "line of communications" when he's 20 YARDS away. If he continues, I'm going to take EVASIVE action. That may mean beating him to my car.
If somehow he caught me off guard and gets close, I'd use the car as a barrier... walk around the car so that the car is between me and him while continuing my verbal commands to get away.
Or it may mean turning around and heading back to the hospital. If he gives chase, then the threat is articulable AND reasonable.
Six feet is a major failure, if that's the first interaction.
I'm not predisposed to run back to the hospital but using the vehicle to keep him at some safer distance is tactically sound.
This scenario is an actual event I experienced in the early 90's. I'll wait for others responses before I explain what my actions were.