On 4: It does absolutely alter balance since you can track the deck and know when you are due for a good result, maybe even a crit. You can 'save' those for your Paladins, making sure you get big smite damage.
Look, I have save-scummed quite a bit in my time. Including in games where the random seed gets baked into the save, like XCOM or Civ 4. There is a lot you can manipulate just by varying the order of actions if you know the random rolls in advance.
To give a simple example: you have a character with a 50% hit chance and one with a 90% hit chance. With normal randomness you have a chance of 45% of both hitting. If you can adapt to the order of random numbers then it increases to 65%.
Anyway, having bad luck is mostly a matter of perception and a lot of fights in BG 3 are effectively over in less than 20 party member actions. If your Hold Enemy has 2 out of 2 enemies save at only a 20% save chance that's still combat changing, and people will feel annoyed about it. So I don't even think it solves the problem you want to solve.
