You can not react all you want, but that doesn’t help anything going on under the surface

Reacting also means any thoughts you may have. You reacted by thinking all of this:

It’s not like we don’t know that. Otherwise OP wouldn’t have the self awareness to [...] behavioral problems.

That's reacting. VERY reacting. Did it solve anything by reacting like that? Telling me all that? Does it fix your problem - the idiots on the road? No. What would fix the idiots on the road? Speaking to your political reps, volunteering or funding road safety charities.

Mindfulness and stoicism is just living with the anger and stress instead of solving it.

No it isn't. I strongly urge you to study it more. Mindfulness is the first and very important step to realising emotions don't rule you. You rule your emotions but most people manage their emotions badly. They fight or ignore them. That's a bad idea because they don't like being ignored, they come back x10. I've done DBT which is like CBT for emotional regulation and mindfulness is a key component. Mindfulness teaches you to detach from your emotional impulses and react more rationally. It's a lot like CBT but it uses mindfullness to help you learn that fundamentally important fact: You are not your emotions.

You don't ignore your anger, sadness, pain, etc with mindfulness, you embrace it.

Take meditation - pure mindfulness - you sit in silence with your eyes closed. Your arse hurts (pain), your back (pain), am I breathing right (anxiety)? I should focus on that (intention), fuck I'm bored (iritation), I'm tired (tired), maybe I should eat (bored/hunger), etc. The simplest, most basic activity you can do is immensely difficult for people to manage more than 5mins of. Why? Because you're governed by your emotions, those drives and annoyances flooding you every few seconds. You realise your mind is noisy as hell but meditating/sitting silently teaches you that you aren't those emotions.

From there it becomes easier to 'pause'* your feelings and make a more rational and useful response. A response that gives catharsis.

*pause is the wrong word. You kindof 'pause' your inner state, step back, assess and act. It sounds overly complicated but like any skill it becomes second nature and instantaneous with practice. Meditation is a form of practice and living your daily life as mindfully as you can is practice.

Stoicism

Is basically CBT/DBT and mindfulness spat out in quote format. Having read the above maybe you'll see that in these Marcus Aurelius quotes:

• “You have power over your mind — not outside events. Realize this, and you will find strength.”
• “The happiness of your life depends upon the quality of your thoughts.” - thoughts, feelings, actions and speech are all different things. You can't control your feelings but you can control your thoughts!
• “Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.”
• “Waste no more time arguing about what a good man should be. Be one.” - to reference your comment: Instead of bitching about idiotic drivers: Be a better driver and do what you can to improve others driving.
• “If you are distressed by anything external, the pain is not due to the thing itself, but to your estimate of it; and this you have the power to revoke at any moment.”
• “The soul becomes dyed with the color of its thoughts.” - embrace your feelings, manage your thoughts.

Recommended Reading:

• Meditations - Marcus Aurelius
• Peace Is Every Step: The Path of Mindfulness in Everyday Life - Thích Nhất Hạnh
• The Miracle of Mindfulness: A Manual on Meditation - Thích Nhất Hạnh
• Dhammapada