As for jailbreaking 2.2.1 on iTunes 8.2, you can't. Simply because apple changed something when 8.2 was made. If you aren't happy with 3.0 and want to revert back to a JB'd 2.2.1, you'll have to download and install the previous iTunes.

iTunes 8.2 is designed around 3.0 more than 2.2.1 although 2.2.1 (non-JB) can and will still sync.