I have been down this dead end road, in< SPAMHATER101 >
some ways it has actually gotten better.
CL now has by dealer categories so you can avoid them by using the by owner option.
I think you are doing a couple of things that although they are not wrong they are ineffective.
Flagging ads in by dealer category is not likely to bring down an ad, possible but not likely.
I would save your flags for the owner category, and when I say save your flags I mean it, there are flag speed limits and you are over the limit if you flag 100 ads in 10 minutes.
I would stop flagging for at least 48 hours then flag no more than about 25-30 ads in 2 hours
and no more than about 50 a day and that might be pushing it.