Cody,
We had luck using the ManualPurge.exe attached to
AKB 31988. Not sure that you can safely "swap" out the old table data with just the newer rows as your DBA suggested. It might work, but then again it might not! I would probably contact Symantec support first to run it by them, or if you're feeling brave, shut down all the ALtiris services, IIS, etc, backup your DB to disk, then proceed. Then start up the processes again with the now much smaller table in place and see what happens if you run a full inventory from a client machine (after modifying some of the .exes on the machine). If it doesn't work, you can relatively safely restore the DB back to the prior configuration.
To answer your question, yes Add/Remove history data is stored in a separate table, InvHist_AeX_OS_Add_Remove_Programs.
I would definitely reduce the number of rows/months you keep in that table.