So, i'm not going to express a precise legal view here (i am sadly too involved, i'm just going to stick to answering more general questions and pointing out what caselaw says), just pointing out your analysis of commerciality as the goal of the first factor is precisely what SCOTUS said not to do :)

I will simply point out, as i did in another comment, that the court of appeals in that case did in fact, claim that because 2 live crew took the heart of the old work, and made it the heart of the new work, that it was not transformative, and SCOTUS said that was wrong.