Sales Tax questions

I have a few sales tax questions. 

1)  Is there a quick and easy way to inactivate 200 sales tax codes and groups that were imported in error?

2) Does anyone else find that the sales tax reports do not accurately give you the information you need without running and combining several searches and reports, or is it just me (I admit we don't charge sales tax a lot, so part of the problem is that I am always have to go back after the fact and try and find customers who should have been charged tax but weren't)

3) If you charge someone tax and then they come back later and say that they are exempt, how do you credit the tax?  I have created a non-inventory line item, but that does not show on the sales tax report.  Do you have to credit the whole invoice and re-invoice for the correct amount?