I'll be interested to see where the new droplet comes out, like you said, hopefully not a third new size.
And good catch! I've added INSTALL MYSQL CLIENT UTILITIES to the script here now so that'll be installed as well.
Sorry about the extra volumes, I'm glad you caught that early before the cost added up too much. DigitalOcean gets expensive quickly when you get to the larger sizes.
RE: SBDS to MySQL in Docker