Stress on front fork from car transport
How much unusual stress are you talking about?  The weight of the bike all on one leg of the fork?  Or the weight of a really large person leaning back against the fork?

If it's just the weight of the bike leaning "wrong" on the fork, I wouldn't worry about it.  That fork leg is built to handle a lot more stress than that in normal riding.

If it's worrying you, you could always pick up a cheap hub and quick-release skewer and put that into the front fork when carrying the bike in the car like that.  That way the stresses on the fork would be shared on both sides and much more match up what happens when you're riding.