A similar topic by Rob, Black Specks on Glass.
We spoke about chips in glass and as far as I know you can't do any thing about scratches and chips but one avenue you could go down and that is, have a chat with one off these companies who repair window screens and see if they can do repairs on windows this is some thing I am looking into if this can be done will open up a new angle to cleaning and repairs,as never heard of anyone else doing repairs.
Hope this helps alan