@retroroscoe I don't have answers to your questions as a lot of people can make it work, I can only share what I've experienced.

Mysql stopped working for us at 5.7 on our 10.12/Sierra Server.

we weren't the only ones (Like i said, you can make it work)
-- https://devmarketer.io/learn/do-not-install-mysql-macos-sierra-how-to-fix/
-- https://serverfault.com/questions/843878/mac-os-sierra-cannot-start-mysql

We moved our MySQL DB to a RHEL box and left tomcat / repository on the MacServer.

HUGE HUGE HUGE Improvement in performance. I suggest getting away from MySQL on the Mac.

Yes, funny enough I had to rollback to 10.12.6 and MySQL 5.6x and it runs pretty sweet.
Was just wondering if any improvements had been made.