Choosing which tapes to pull for offsite storage

So you are creating a Custom report that will certainly show you what you need, though as you've seen these can get quite complex quite quickly.

One alternative would be to look at using Vaults. When you create your Media Set, create a new Vault first.and get the Media Set to use that vault. My reasoning here (because it could be argued this is over-complicating things) is that you can simply run one of the standard reports that are pre-setup. eg Media - "Move Media to Vault" (to show 'what media should be moved to a vault')
Refer to the admin guide (Tape Storage chapter) for more info   https://www.veritas.com/content/support/en_US/doc/59226269-152612234-1 

Or have you tried the "Recently Written Media" standard report rather than creating a custom one?

There are a lot of options/filters available within reports, and are no additional add-ins available (3rd-party or Veritas ones) as far as I know.