Thanks for the instructions for newbie Mastodon instance admins like me!
All went well. I did add one thing prior to doing the backups - I took the files storage down to just 2 days to cut the amount of data an files because I typically run like 7 days, doubling that for backup gets me close to my service level limits.
RAILS_ENV=production bundle exec tootctl statuses remove --days 2;
RAILS_ENV=production bundle exec tootctl media remove --days 2;
RAILS_ENV=production bundle exec tootctl preview_cards remove --days 2
This got me down to like 40gb or so - so doing the backup still left me with enough space. Thanks again for the help and assistance through all this! Been fun running my own server on Opalstack.