You're argument is that Iran cannot be trusted with nuclear weapons beacuse they are uniquely horrific. Yet you are unable to elucidate why or how they are uniquely horrific compared to other nuclear powers.
In fewer words, you are unable to support the core pillar of your argument.
I disagree here actually. A balance of power is more stable and less likely to create conflict. That's a fairly conventional argument in IR circles, even outside of realists. With nuclear weapons specifically, a first strike isn't actual deterrent, it's a second strike. Having a first strike is actually more dangerous.
Now, whether or not a nuclear Iran and Israel would create a balance of power and more stable Middle East is a more tenuous question. I think it would stabilize the region some by deterring Israeli recklessness, but the challenge is Saudi Arabia and its allies. More specifically, the goal should still be that Iran doesn't get nuclear weapons, but that means hard tradeoffs and concessions from the US and Iran. Otherwise, Iran will just pursue them as there's no real downside at this point.