RT, I think you're working too hard. This board is superior to anything else out there, even with it's occasional breaks from civility.
I wouldn't try so hard to lay out the ground rules for decorum. Just let the consensus that usually arises (as in, the group beatings that lurker trolls usually invoke) take care of the situations as they arise. Sure, sometimes things take on too much of an aggressive tone and need to be nipped, but usually it's self monitoring. By and large the people here are grown up enough to know how far they can go before the thread becomes out of control.
Heck, if you're not sure what the masses think about a specific thread as to whether or not it should continue, just ask! Personally I think a vast majority would probably have the same opinion on where to draw the line, whose posts are over the top, etc.
For the individuals, I would suggest that before you go off blasting someone that has jumped on your case, you ask them specifically if they really meant what they said, and include details. Ask for clarification, as in "Did you mean to say that just because I XXXXXXXXX, I should always ZZZZZZZ?" Usually if they're reasonable they'll back off because they realize they went beyond the limits of a reasonable debate.