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Read CE again, guys

Not the TRUTH of God but the truthFULNESS of God, not what He revealed but His truthfulness in the revealing of it

extrinsic because the truth of revealed truths cannot be known intrinsically since our intellects cannot grasp them as intrinsically true by themselves without the authority behind them

the FAITH is not the RULE OF FAITH

If some sources use the term faith loosely as rule of faith, it's because it's speaking of it materially rather than formally, just like you can consider faith materially as the propositions believed or formally as the supernatural virtue of faith

It is really all right there on the first cited paragraph:

The word rule (Latin regula, Gr. kanon) means a standard by which something can be tested, and the rule of faith means something extrinsic to our faith, and serving as its norm or measure. Since faith is Divine and infallible, the rule of faith must be also Divine and infallible; and since faith is supernatural assent to Divine truths upon Divine authority, the ultimate or remote rule of faith must be the truthfulness of God in revealing Himself. But since Divine revelation is contained in the written books and unwritten traditions (Vatican Council, I, ii), the Bible and Divine tradition must be the rule of our faith; since, however, these are only silent witnesses and cannot interpret themselves, they are commonly termed "proximate but inanimate rules of faith". Unless, then, the Bible and tradition are to be profitless, we must look for some proximate rule which shall be animate or living.

It is extrinsic to our Faith in the sense that it is an external standard by which we can measure or test the truthfulness of the Faith, the "ultimate" rule thereof: the truthfulness of God in revealing Himself. Now, both Scripture and Tradition are the (proximate) rule of our Faith; but since they are "silent witness and cannot interpret themselves" (inanimate), an animate or living proximate rule of Faith is needed to continue for each coming generation: this is what the teaching Church is, the Magisterium.

Again, it is a constant teaching of the Church that although not everything emanating from a General Council is infallible; it cannot be harmful for the faithful either.

If it's not infallible, then in theory, it could be an error, and hence harmful.  Where is this 'constant teaching'?

Just because the Church says that:  "All ecuмenical councils HAVE been infallible", does not mean the same thing as "All ecuмenical councils ARE infallible".

The fallible portion of the narrative must necessarily be in accord to the constant Magisterium of the Church.

This is a contradiction.  You're saying that the fallible portion is infallible (because the "constant"/universal magisterium is infallible).

Furthermore, the detailed compartmentalization is unnecessary.

I don't follow.

An ecuмenical Council is an Act of the Magisterium.

Agreed.  It is an act of the ordinary magisterium, which is fallible, UNLESS what they teach agrees with the UNIVERSAL magisterium (which is 'what has always been taught').

The Magisterium cannot defect.

The UNIVERSAL magisterium cannot defect.  The ordinary (or 'merely authentic') can.

Even if you want to argue that VII is not infallible, but fallible, it could not have ever been detrimental or harmful to the faithful, once promulgated by legitimate authority.

Same contradiction as above.
Further, you are falsely equating the word 'ecuмenical' with the nature of infallibility, which is wrong.  They are separate attributes.  Ecuмenical just means the council represented all the diocese of the world, in contrast to councils which are locally focused.

A council's language and form MUST follow procedures in order to bind the faithful.  V2 is constantly using passive phrasing and non-authoritative language, which 1) does not indicate apostolic authority, 2) does not promote clarity in its 'teachings', 3) does not bind anyone to follow anything.  It was meant to be ambiguous!  And ambiguous language is NOT BINDING, nor is it legally valid.  And certainly, it is more than fallible, it is erroneous.

Here is the opening sentence from the 1st Session at the council of Trent (and we all know that Trent was an infallible council):

Doth it please you,--unto the praise and glory of the holy and undivided Trinity, Father, and Son, and Holy Ghost ; for the increase and exaltation of the Christian faith and religion; for the extirpation of heresies; for the peace and union of the Church; for the reformation of the Clergy and Christian people; for the depression and extinction of the enemies of the Christian name,--to decree and declare that the sacred and general council of Trent do begin, and hath begun?

Is this infallible?  yes/no.