Does my public feed go down too?

No — and this is one thing that never breaks. If your Benecaster licence lapses, your private subscriber feeds stop first (after a grace period) and then stay off until you resolve it. Your public feed — the ordinary, no-token RSS feed your show is listed under — keeps serving normally throughout, both during the grace period and after the cutoff.

The reason is deliberate: a lapsed licence drops your site to exactly the free WordPress.org version of Benecaster, and that version serves public feeds. You lose subscriber delivery, not your podcast. See Payment Failure and Recovery for the full timeline.