One of eBay's other rules is that an account can't be closed until at least 90 days have passed from the last transaction. I think that will probably give you enough time to think about whether you want the impact of that negative to include the closing of you otherwise successful trading. (And yes, best to remove that line about closing your account - you can't do it now anyway, it's irrelevant to potential buyers and will probably turn them away, not to mention reportable. The last thing you want is a neg and policy violations).
I know negs don't feel all that flash, more so if you think it's unjustified and eBay won't remove it, but the policies are there for a reason and sometimes they cause consequences for the wrong people. How drastic those consequences are, though, depend on you - like the others have said, if all your other sales and buyers have been great, there's no need to end it all so dramatically. ๐
