@danaxf4 First, thanks for getting me to think about this passage, which was quite thorny and got me thinking about it a whole day.
Now, let's break this down.
In the first clause, it's a simple correction, but I disagree with the strength of your choice of conditional. I did forget to account for it, but として isn't a plain "if", but a foregone assumption/conclusion, so I corrected it to "seeing as".
The second clause is where we diverge. You probably interpreted this as Yona seeking to mete out retributive justice to Soo-won due to her use of 溜飲を下げる, as opposed to the "passive" 溜飲を下がる. However, I stand by my choice of words (though I toned it down to "derive satisfaction" instead of "rejoice") based on the meaning of 因果応報. In all sources I've checked, before and after your comment, I found this syntagma to mean not the kind of retribution associated with revenge, but a karmic, "divine" justice akin to the English "chickens coming home to roost". So I'm convinced she's referring to his dying of his illness, in which she has no part. A senpai who helped me think about this found a sentence with 下げる that has a passive meaning, too.
As for the part on mourning, 哀しむ can mean both, so it's your preference versus mine. I think she refers to his fate and present state, you think she refers to after he dies. As I'm the one translating this, I'll stand by it.
The last part is the hardest one, though the structure of the sentence in so simple. In all likelihood, we're both wrong.
Both you and I made unwarranted changes of frame of reference. You made Soo-won the target of her 待ってと願って. And I used a rare meaning of 待つ, "to trust, to place hope in". In any other circumstances, I wouldn't have given your translation two thoughts as the correct one, and it's probably what I'd have written, too. The problem is,
Yona has never asked Soo-won to wait for anything in the entire manga. So 願う in this sentence can't be "to ask, beg". It has to be "to wish for, want", which is what I went for. Unless it's not Soo-won whom she's asking.
My senpai came to the conclusion that, since no change of frame of reference happened, Yona's still talking to herself and about herself, as in the previous page. I agree with his interpretation. Thus, the likeliest translation is "I just went and told myself to wait". May I also add that your version failed to account for the negative connotation of てしまった, which means Yona thinks of that action as ultimately mistaken or a cause for regret.
It's still a little vague what she means by that. My guess is that she regrets having convinced herself to adopt a wait-and-see attitude regarding Soo-won (perhaps instead of seeking to confront him about the past sooner, or maybe regarding her feelings before he betrayed her). But it's okay, it's probably vague and unclear for the Japanese readers, too.
I've made a v2 here reflecting these changes.
Well, I learned something new, thanks to you and senpai.
As for my own opinions and notes, I respect your view on them, but I'll ignore it. I like to write my thoughts in the margins when I'm translating. It's one way I enjoy this hobby.
P.S.: I prefer discussing translation issues in private. Shoot me a DM next time, please.