I'm not sure I could have done anything different.
You wrote a life-lesson of motorcycling within your post....
The only clean spots were where car tire paths were.
Ride where the tires of cars usually are, especially when anticipating gravel.
In the early spring and often when I am on roads I am not really familiar with, I tend to ride through curves where a car's tires would be, and try to keep from clipping the apex in the curve because that is the most common location for gravel to be kicked out of the shoulder and into the curve. If you are riding too fast to be able to keep that line through the curve...slow down.