I called the awning manufacturer with the exact problem. They were emphatic not to use anything but mild soap with water on the awning. A couple of solutions: 1)Let it go or 2)Let it go for another year and then see if it hardens enough that you can squeeze the awning and break the pitch off.
I think that there are instructions right on our awning to only use mild soap and water, as you say. I guess I would let soap and water sit on it for a while. Then scrub.
I use the 303 Protectant on the awning after wash. We need the UV protection out here in AZ. It makes it easier to wash as stuff doesn't seem to stick to it when it has been treated with the 303.
To remove pearut butter use red squirrels, chipmunks, woodpeckers, and for A final cleanup: ants. While they are working, go to town and get patching material and a needle and thread or a speedy stitcher.
Dave