Whose content or which content

"A pertinent way to analyze this broad phenomenon is to subdivide its analysis in three sections which content is partly based on the updated findings...".

Until this passage, I was 100% sure that in this case I had to use whose instead of which.

An entry on Merriam-Webster goes like this: (Content) a : the matter dealt with in a field of study … the content of sociology is inexhaustible … — Franklin H. Giddings

I think the cited context is a relatively uncommon literary / dated / formal / archaic construction as used here...

The earliest people in the earliest ages, though they were rude and uncultivated, were eager to know the truth through study, the which desire is still, as we see, natural to every one.

...where the article (the which) is normally included where there's a specific noun identified immediately after which. In many such contexts you could do away with the noun (content in OP's context, desire in mine) completely, but in both these examples that's a little problematic.

This is because the exact referent of which hasn't been precisely stated in preceding text (which content = the division of the analysis into three sections, which desire = that of people eager to know the truth through study). The writer needs to insert a clarifying noun so it's obvious which "which" is being referred to.

It's not all that easy to find written examples of [the] which noun, but here's another one...

the young buckramite rudely seized him by the collar; which rudeness he returned of course.

Which is an interrogative pronoun. In this form the sentence makes little sense since it looks like you are asking for something in the sentence (which content?). It can be used as a relative pronoun to refer to the precedents of the sentence. The precedent would be for instance the three sections

However, whose is the possessive case of which and who. Since the content belongs to the three sections and you want to make a reference to precedent sections, then you can use whose to form a more unambiguous and clear logical sentence.