This is really useful information for me thanks again. I did not realise that a warning would not be triggered at any speed below the lowest figure, having this speed set high may not be a good idea for something like a red light camera, not that I am suggesting driving through lights at red!
I wonder if the person that wrote my original warning_distances string understood what they were writing as surely the 70 and 90 speeds are not necessary as you describe that anything over 50 up to the higher figure is the same distance.
Anyway I will look for other .ini files and report back once I have had time to test. Meanwhile I second your request for someone to enlighten me about the other questions.