Tablo Ripper processes recordings in the order they were recorded. While I haven’t stress-tested it to the extent that you are now, there are no “built-in” limits to the number of shows it’ll rip.
The sheer number of shows probably makes it difficult to manually reconcile what’s been ripped already, but unprocessed shows should show up as “new” if you apply that filter. I’m in agreement with @LJ_LongWing, if you can’t watch them, you won’t be able to rip them.
It doesn’t matter “how” you watch them, it’s more a matter of “do they really exist” on your Tablo. Occasionally, the Tablo recording list won’t match the data actually present on your hard drive. If that happens, it may appear you have shows that aren’t actually available to watch/rip.
Hope that helps.
PS: @Nilex is correct - I only monitor the primary TabloRipper thread. That’s how to get my attention when you have questions.