From looking over the lyrics, it sounds like the subject is someone else and likely one person. The song is about this person, who is a Philosophy NEET, which is the truly ambiguous part. How do you define a Philosophy NEET?
A good portion of the rest of this answer will be rooted in some opinion.
From my take, a Philosophy NEET I dissect to be a specific kind of NEET. Defining NEET first as Not in Education, Employment, or Training, and the fact that a common typing (mostly true of English but sometimes true of Japanese as well) of (object)+(subject), means that the subject is a sort of fan, maniac, otaku, or the like, of object. So, in this case, the NEET is a fan of philosophy, and is probably a philosophical thinker, however the person is also a NEET. Therefore, Philosophy NEET.
If you consider the repetition and the fact that it is the first sentence in the chorus for the song, it can be construed that Philosophy NEET is what the singer is calling this person. And so, she is calling a thing by its name.
So in the case of the first example you gave, I might render it as:
哲学哲学哲学ニート
(Hey,) (Philosophy-philosophy-)Philosophy NEET
揺れる幻に酔いしれて
(You're) drunk on a swaying illusion
As for the sentence where you're having confusion:
ああ哲学哲学哲学ニート
(Hey,) (Philosophy-philosophy-)Philosophy NEET
僕は迷い込んだ幻想{ゆめ}の中
I'm within an astray illusion*
- Note the Kanji used spells illusion, and is commonly read 幻想{げんそう}, but here it is read ゆめ which is normally spelled 夢 and means dream. This is a form of parallelism.
This sounds to me like the singer is becoming influenced by the Philosophy NEET. Compare this line with a similar line earlier in the song. First she sings, towards the beginning:
君は迷い込んだ夢{ゆめ}の中
You're within an astray dream**
- Note the Kanji used actually spells dream in its normal spelling.
So, the subject never changes as being someone else, the Philosophy NEET. The one line where the singer talks about herself is telling the subject what's happening to her.
EDIT: Forgot to mention. I consider each of these one sentence, but two separate expressions. As in, not "Philosophy NEET is drunk on a swaying illusion," for example, but "Philosophy NEET, you're drunk on a swaying illusion".