Man do I got my work cut out for me. I'm taking notes on everything you've found so far and will be going in to fix up Namingway Edition as soon as I get free time. Currently my family and I are moving, so I won't be able to devote time to it until after we settle in. Thank you so much for pointing these all out!
I figured it would be best to do this testing now while you are still active, in a year or two you might be done with this hack/translation and no longer working on it, who knows, I would like to help fix as many problems as I can before it is finished for good since every hack/translation eventually stops getting updated at some point in time, rarely do they remain active for more than a few years. Even then if someone else takes over and makes an addendum patch a decade later to continue work fixing things up, well, that is too long to wait!!
Anyway I just found another bug/typo involving hardcoded names (my secret is I am playing the game with a TON of Pro Action Relay codes and cheating to make the fights REALLY easy so I can get through the game VERY fast to view as much text as possible, I am not THAT good at this game that I can get through it so fast without cheating). OK so this is the exact same type I found earlier with Rosa and Rydia having their names hardcoded. In the boss battle in the top part of the Tower of Babil, not the 2nd one with Rubicante but the 1st one before with Edge’s mom and dad, the Eblanese king and queen (and you are correct in calling them Eblanese, I looked it up, the latest translations use that and your enemy names are really good too, very true to the PSP translation), there are some more hard-coded names of a party member: Edge.
First, before the fight, the Queen says “Edge...come...” This is after several lines where Edge has his correct Namingway-chosen name said. (Yeah, I went back to the Namingway in the Cave of Eblan among the Eblanese to change Edge’s name prior to this fight, I changed it to Sasuke from Naruto because he is a ninja whose parents are killed and who gets his powers from his rage, I am really going with this anime character theme.) So anyway since I was using the name Sasuke she should have called him Sasuke in that line, earlier in the lines before the fight he did correctly get addressed as Sasuke by the king. Anyway this is where she asks him to come “To HELL!” Then a little while later during the fight, after the parents recover their minds and Edge is correctly called by the name I changed him to, Sasuke, several times, the king says his last line, “Take care, Edge.” right before dying, a second case of Edge being hard-coded instead of using Edge’s current name. After this, everyone goes back to correctly calling Edge by the new name I picked for him, Sasuke, again.
Oh and one more... 2 items have inconsistent names, in the side-quest involving the frying pan used to wake up Yang that you get from Sheila. First you get the frying pan, when Sheila gives it to you in Fabul it is called “FryinPan” in the dialogue but in the inventory it is “FryingPan” with the ing taking up the space of 2 letters instead of 3. So the dialogue version of the name of that item should be the same as its inventory version. Later on after you wake up Yang and get the Sylph summon for Rydia and go back to Sheila and return her frying pan, she gives you something identified as “Cleaver” in the dialogue but in the inventory it is called “Kitchen” next to a knife symbol so basically it is a “Kitchen Knife”. Now this is a recurring item throughout the series, usually the PSP names for things are best for Final Fantasy IV things, I think, and the PSP version calls it “Kitchen Knife”. It is called “Cleaver” in 2 later games that I know of, Dissidia Final Fantasy and Dissidia 012 Final Fantasy. In Final Fantasy VIII and XI the name is “Chef’s Knife”. But, I think, to be consistent with more recent translations of this same game Final Fantasy IV, “Kitchen Knife” is best, or a knife symbol with the word “Kitchen” after it, as appears in the inventory, so the use of “Cleaver” like in the dialogue upon receiving this item from Sheila, I think, ought to be changed to match the name “Kitchen Knife” used in the inventory. So basically in both of these cases the inventory names are correct and the dialogue names should be changed to match them, I think. (The full name of the frying pan in Japanese is “Ai no Furaipan”, or “Frying Pan of Love”, but we do not have enough room for such a long name, but still, I think the Japanese name is very cute. But much too long a name to fit into an English version of this game, I suppose that just has to be lost in translation.) Anyway there is a good guide to names of things in different translations on the Final Fantasy wiki here: https://finalfantasy.wikia.com/wiki/Final_Fantasy_IV/Translations
(I would go with the PSP names in the rightmost column whenever possible and it is very clear on “Kitchen Knife” for the throwing weapon Sheila gives you at the end.)
Oh and this side quest has to be done at a very specific time in the story, you can only start it after visiting Yang in the Sylph Cave in the Underworld at least once which means after getting the red airship upgraded to fly across lava, the one that later gets a drill added to it so you can return to the Overworld, after Kain leaves at the Sealed Cave. But to finish it you need to be able to visit Yang’s wife Sheila in Fabul after seeing him asleep in that cave to get the frying pan, then return to the Sylph Cave to hit him with the frying pan and wake him up and get the Sylph summon, then return to Fabul to get the kitchen knife after returning the frying pan to Sheila. Anyway the problem here (not with your translation but with the game) is you have to do this BEFORE you go to the moon and recruit Fusoya into your party, and do most of this quest with only 4 members in your party: Cecil, Rosa, Rydia, and Edge (no Kain or Fusoya). Because Kain leaves before you can get anything from Sheila, and once you get Fusoya it is too late to finish this sidequest. Anyway to test this out that is important to remember, to delay getting Fusoya on the Moon until after you are done with all of this. This is very easy to get wrong by having Fusoya join too early since everyone is telling you to go to Mysidia and take the Lunar Whale to the Moon and this can easily mislead you into missing this sidequest entirely. Regardless I am glad that you gave Sheila and Joanna their proper names instead of just calling them Yang’s wife or Rosa’s mom, I definitely agree with using their correct names like you did.
One last naming issue: the cave/passage that goes to the Feymarch (you have the Feymarch correctly named) is called “Passage of the Eidolons” in both the PSP and 3D versions so that is considered the canonical name. You have it called “Feymarch Passage”, which does make it a bit more obvious where it goes, but this is not the standard name in recent English official translations. Also “Passage of the Eidolons” is closer to the literal translation of the Japanese name for the cave, “Genjuu no Dōkutsu”, which literally translates to “Cave of Phantom Beasts”, making the original SNES translation “Land of Monsters” not that far off although I would not recommend that, I think going with the standard PSP and 3D translation of the name is best. If you really need to save space in the name you can just shorten it to “Eidolon Passage” from “Passage of the Eidolons”, that is about the same length as “Feymarch Passage”, but it is better not to shorten it if possible.
Anyway I would not be able to find all this so fast without using PAR codes for cheating to get through the game much much faster... which I am doing for testing purposes, I have beat this game in the past several times WITHOUT cheating so it is not like I don’t have the ability, I am just trying to find typos in the script or other bugs faster. And yes I am aware cheat codes can create bugs that do not occur in the game unless you cheat, I am very careful about that, I only report genuine bugs to you, the stuff that is caused by cheat codes I fix myself by either reloading the game from before I used the cheat codes or using more cheat codes to clean up the mess. I do not use any PAR codes that are even remotely plot-related or that are known to cause glitches, I just use safe ones, to max out experience, stats, levels, money, etc., give people their best equipment and all their magic, and make my party basically invincible.