I think part of the issue you're running into with this is that you're kind of taking an "all or nothing approach" and if we're to approach this with Buddhism in mind (I'm gonna switch to that cause I'm a bit more familiar but the parallels with Stoicism are still there), there's the whole "middle path" and "avoiding of extremes." With traffic in mind, who's to say being cut off warrants any response more than knowing that it frustrated you, appreciate the fact that you can still be frustrated, and let go of the moment. I'm not necessarily saying "no harm, no foul" but sometimes it's better to just not act at all. Now say on the other hand, you're being mistreated by a co-worker and they're creating a hostile work environment for you and your other co-workers, that's a situation that requires a thoughtful reaction.

Similarly for generosity, it's not an all or nothing approach. It's important to give, but it's also important to not give so much that you burn yourself out, put yourself in financially, emotionally, psychologically precarious positions.

Desiring not to be a jingoist or loving a country is a personal judgment in itself. What flaws you might find where you live might be different from which flaws somebody else finds. American exceptionalism, for example, might be good for the economy. Would you go to war to defend your country? One could argue the most compassionate response is to refrain from killing, always, and not to expose yourself to situations that could get you killed. Another might call you a coward who's okay with fascism spreading.

I feel like I could answer this from a Baha'i perspective, but since that's not the philosophy discussed here and I'm starting to doubt what I understand of Stoicism, I don't have a good answer for this. I think the best answer would to circle back to Stoicism's emphasis on personal, independent thought and say "you gotta analyze the situation and come up with your own answers."

I don't disagree clear thinking and rationality are possible and desirable, but it becomes difficult outside of formal logic and mathematics.

It isn't, but you gotta factor in concepts of what is compassionate, what is just, etc. With that in mind, to the quote you selected . . .

Stoicism teaches the development of self-control and fortitude as a means of overcoming destructive emotions; the philosophy holds that becoming a clear and unbiased thinker allows one to understand the universal reason (logos).

Overcoming destructive emotions doesn't mean not feeling them, it means knowing that they're there, that they make you vulnerable, that they can cause harm, etc. It means empowering you to make the right choices not because they're absent, but because you can handle their presence.

Determinism is partially nonsense in my opinion. It's a good way to fall in an apathetic or fatalist mindset.