I can't figure out the meaning of the chorus from the song 俺はやる by Wanyudo. Particularly I have a problem with the word カス.
The context is as follows (someone transcribed the full lyrics here, the link contains also a live performance of this song without the need for Spotify account):
From the first phrase (口だけのカス) I guess カス is a noun and it might be used in the fifth meaning here: dregs (e.g. of society); scum; dross (and etymologically coming from カストリ文化) for someone who lives only from "their mouth", i.e. this rapper.
I imagine the first line (口だけのカス朽ち果てろよ) is something that he hears (from imperative form of 朽ち果てろ) and the meaning of what follows and the chorus would be an answer to it - something like "this is how I live, this is the way of カス."
Is my interpretation correct?