Bruce, sorry about what happened. I had two similar situations, the last one allows me to offer some advice. My first was when my 99 Box got keyed. But, that was "easy" to fix - take it to a body shop for painting.. My second situation is more like yours. My right front fender has about a 100 very very small, how can I describe them, etched spots. I have no idea what happened, but they are almost microscopic spots where something ate through the clear coat and paint. I can feel them with my finger nail to know they are not raised, but indented. They can only be seen from certain angles, but when they are visible they are pin point sized black dots on (in) a silver fender.
OK, so how does this help you? I took my car back to my body shop. I had used them several times in the past (Boxster twice, Civic once). It is a small manager owned shop with a great owner and tech staff that I trust. He had one of his body techs spend about an hour going from less to more aggressive means one one of the spots to see if something could be done short of re-painting the fender. Nothing worked. But, this is something you should do. Take it to a pro. They may know what is on your car, have some related experience about how to deal with it, and certainly have the tools and chemicals to try to see what works or doesn't work to get it off w/o harming the paint. My body shop did the hour worth of work for free, as I said, nice place. But, even if you pay for an hour of work, say $100, to get a pro to see what works/doesn't work, it may be worth it. From there, if there is solution to the problem that you can do at home, you will know how best to tackle the problem.
Goo luck.
1999 Arctic Sivler/black/black (sold)
2008s Silver/black/black - so predictable
2011 Outback
8/24/2011 first Grandson