Glad my comments helped some. I'll see if I can sort out a few of the last questions you have.
You seem to be pretty good at doing research on the internet, as you've come up with the names of a lot of the town areas and such, so here's a tip to take you further: you can search the name of a game along with 攻略 to get walkthroughs and databases about games. ポイズンピンク 攻略 would do for Poison Pink. I get
this website for the first result on Google. You can put the whole page into Google Translate, or you can take text you might have from other sources, like 第2階層 夢幻の天空 which I gave you earlier for the area name of Aether, and use Ctrl+F to see if you get anything. On that page, you'll be taken right to a list of the area names. 聖皇の祭宮 and 閻帝の万魔殿 seem to be the area names for the 3rd strata, so it's certainly not "Lumen" and "Tenebrae" written out for those two, but something a little closer to "sanctuary" and "purgatory" respectively.
I don't say this to get you off my back, by the way - more about teaching a man how to fish and all that.
Since you seem interested in version differences: during the first battle in Besek on Thage's story in Eternal Poison, Retica asks "Why do they keep talking about your librum?" In Poison Pink, this is
おい、魔神達がリベルって呼んでるその本は一体何なんだ
Thage also says "There's no other librum like this one in the whole world."
そう、コレは私の特別製、世界でたった１つのリベル
リベル, riberu, is in both sentences, so Poison Pink refers to it as liber, not librum. Now, having taken a couple of years of Latin in high school, I know that librum is the accusative case of the word liber, so it would be the direct object of a verb. If you're going on strict Latin grammar it may seem weird that the localizing team chose librum over liber, but maybe they felt it sounded more like a thing, or more Latin... not sure
Regarding the name Isapolis... given that the Wikipedia page lists the proper names for the other areas in Poison Pink's town, it's doubtful the town itself has one. After the first battle in Besek on Thage's story in Eternal Poison, Duphaston explains "Besek appeared in my domain, engulfing my fair town of Isapolis." In Poison Pink, this is
実は、ベセクが現れたこの場所は、私の領地だったのです
この場所 is "this place" and 私の領地 is "my territory". That's all Duphaston really says about the town. Nothing like 街 or 町 is ever mentioned, nor is イサポリス (which would be Isapolis). It's doubtful the town has a proper name, but again, I haven't been through the whole game. At any rate, it's your best guess as to where the localization team came up with Isapolis.
As for ノリのいい曲, I guess the beat of a song is the easiest way to explain the song having a "nice feel" or being "easy to get into". I believe the term comes from Noh theatre, in which ノリ, nori, describes the tempo. Bad nori, ノリがわるい, is difficult to get into, while good nori, ノリのいい, is easy to get into. When you add 曲, it refers to music. So, no, the phrase has no direct correlation to oldies.
If I one day get a copy of this soundtrack, maybe by then I will have deciphered what 幾夜寝覚 means, if it's not just meant to be a name. It could just be ikuyo nezame, I guess, but I kind of doubt it. Anyway, I hope that stuff helps
it's been nice talking with somebody about this game. I haven't played it in a while, I should get back to Eternal Poison and finish it off.