The awning bracket attachment on the roof and the skylight over the shower forms a dam that directs water off the roof at that point. Apparently the screws were not sealed as you both have experienced.
I have used the windshield cover on a class C I had (the '85 I believe). I would think that leaving it on would leave it so dirty I might not want to leave it in the garage while we're traveling. I certainly wouldn't bring it on a trip.
I live near a construction company that does not have a paved lot. Clouds of dust roll over the neighborhood when the trucks cruise through the lot. All of this dust sits on my RVs until the morning dew. I used the gutter across all of my windows on the 5th wheel so I didn't have to wash the windows constantly and it worked exceptionaly well. I even formed it to follow the round corners of the windows. It's a little tricky to install. It's best to let the gutter hang and relax for a week, clean the location with acetone and alcohol, and then get an assist with a heat gun when installing it, especially on the tight radius of a window.