I am not that sure about the first point...
I mean, some things change, that's why we can talk about "fantasy", for starters.
And... if some things can change, why not the basic mechanishm of the world and society?
A while ago I played a game called "Final Fantasy Tactics advance". It was a game where you would build a clan of soldiers and battle other clans. The thing is... there was this "special magic" that allowed everyone fight to the death but without dying in the end.
That actually led to a society based on violence... but said violence wasn't such as a drama as the real world. I mean, people even dueled each other for fun. It was a sport, even.
The "tone" of this game was kinda light-hearted and it actually seemed to encourage you to pick up a sword and become an adventurer yourself.
So yeah, what I want to prove here is... that reality, with the corresponding "tone", can be shapeshifted a lot when it comes to fantasy, up to the point of bending basic laws of reality.
What I mean is... when it comes to fantasy worlds, I think that the "tone" is the most important part. It is what will define the nature of this world and, also, the criteria we should follow to judge it.
As for the second point... well, yeah. Building a fantasy world isn't easy, and maybe these mechanics you break lead to worse consequences. For example, in the game I mentioned earlier... well, let's just say that crime was at its highest rates and people, even if they didn't die in combat, they suffered.
But, back to the tone... maybe this fantasy world's "tone" could have defined that there simply are "not" these consequences. Catch what I mean?