Thanks for the response!
You are right, it is a small board, and the day may come where a forum-wide digest may be multiple pages and cumbersome to read. But at least the user will still hold the power to unsubscribe to individual forums or the email all together, so for now the concept suits our needs
I've been slowly trying to work with the MySQL queries in the functions_digest.php to get a better understanding, but still hitting some questions. And as I dig I learn a little bit more. I imagine I'll be back with some specifics that I can't answer myself.