See you are having a hard time getting anyone to respond. Maybe because no one feels comfortable (me also) with a simple yes/no ... etc.
In previous posting concerning config (my.cnf) see the default engine set to MyISAM? That would apply to new databases created after that setting entered into config. Higher versions of MySQL the default now is InnoDB so no reason to have that setting.
The setting changes you are asking about ... for the most part ... yes.
Especially innodb_buffer_pool_size=1G and innodb_buffer_pool_instances=1
If you run MySQL tuner again after a days usage, it might have more/less/changed recommendations.
What you are using in Moodle ... quiz ... is heavy processing ...
Question: is/are the quizzes set up to display all questions in the quiz on a single page (100 questions as an example)? If so, very heavy processing and thus just a few users attempting to take might see that error. Solution: break apart the quiz. 100 question quiz .. show 10 at a time ... now that value of 10 is an example here. Your server/usage might be able to handle more or less.
Suggest, for now, running MySQLTuner as super user often ... at least once a day to see if changes to settings have not had un-intended consequence ... rather than improving .. gone the other direction.
No pat answers can be provided ... every server config different and unique.