Export data is not guaranteed to be importable in different versions of TSM. That's why you should keep the install version. You don't need the database, you can just import it, I was wrong there.
If you have a compatible version of TSM still running, you can import into that, but if you upgraded and the new version won't import the old data, you'll need a temporary server. You can install a blank db on that one. (It'll come with one even!)
Yes, you can checkout the tapes, but the data will be subject to expiration, possibly reclamation, and you'll need to move the data onto its own tapes by hand.
Archives put quite a strain on your database for stuff that's (almost) never used.
To me, it sounded like it would be most convenient to take the data out of your current TSM environment. But that way, you're not entirely futureproof for restores.
Choices, choices .. you'll have to weigh the costs and benefits for you.
(I think it's a **** shame you can't generate backupsets with TDP data, but it can't be helped. You might dump flatfiles?)