Can I sell audio I make here? Do I owe attribution anywhere?

You own what you generate: commercial use, worldwide, no watermark, and no attribution owed to us anywhere. Sell the audiobook, monetize the channel. The one responsibility that stays yours is cloning consent: if you clone a voice, it must be your own or one you have permission for, which you attest when you create it. The full pledge is on the ownership page, written in plain language on purpose.