If you can't properly define the terms you are using in your instructions, the instructions are meaningless. You don't need to have paragraphs on definitions, and you shouldn't unless the topic is about a certain term.
I don't necessarily agree with that last tid bit. Side characters can certainly change things, they are just not as important to the story as a whole compared to the main cast.
However, unless an author intends for a side character to become part of the main cast, then what they change should...
I mean, what isn't problematic about Game of Thrones? The Bible (tmk) never goes into explicit detail about sex (except for that one chapter where it has some...interesting descriptions) but GoT is just wild.
No, I don't think positivity, in general, can be toxic. I think positivity, where it doesn't belong, can be toxic. People can't always be happy or outgoing and forcing that on them really just gets you the opposite effect.