Just one thought regarding the poison damage:
I also think that the damage done by poison should not be based on the character level but on the poison resistance. However, as an idea, what about introducing different kinds of poison into the game? I mean, in real life there are poisons of different strengths (ranging from just causing the nausea to deadly ones) - so why shouldn't such a system be also implemented into the game?
The general reason is because if games treated poison more like real-life, then it would be excessively complicated.
You should have quoted my next sentence as well

I am not actually proposing that Larian introduces something like "pink" poison for low-damage and "green" poison for high-damage. What I am saying is that the poison-damage inflicted could be based on the level of the creature (like level 3 zombie and level 5 zombie) - with the ostensible explanation that a high-level zombie was rotting longer than a low-level zombie.
This would not be level-scaling on the character's level but would be rather based on the mob's level. And this would not even be a new unprecedented system in D:OS - I mean right now the HP of mobs and their physical damage output is also based on their level (and their weapon), isn't it? Generally speaking: higher level mobs -> higher damage output. So, why shouldn't this system be also extended to poison?