Sounds like something may have etched your windshield, and knowing what is hard to say. Given that you've tried abrasives (which is not really a good idea on a polished glass surface) look at one of the polishing compounds that's made for glass and follow the directions for the product you buy. There's also some YouTube videos out there on cleaning up glass surfaces. This link is just "glass polishing compound" - https://www.google.com/webhp?sourcei...ing%20compound