Yes. And with the paragraph and conclusion of Vatican I, you are not allowed to reach a conclusion different from the teachings or ex cathedra or extraordinary magisterium findings of the Catholic Church. Correct?
For example, take the Catholic positions on communion and Mary's eternal virginity. The former mandates that there is only a literal interpretation; symbolic is not allowed. The latter demands symbolic/inferred only, literal is not allowed.
The Catholic Church has essentially dictated when a person must interpret Scripture literally and when they cannot. And any interpretation to the contrary - even if there is a reasonable logical support for that contrary conclusion - is heretical and must be avoided.
How is that not the Catholic Church dictating how scripture must be interpreted? We have the Catholic Church explicitly stating that you must follow the teachings and dictates of the Church, and that you cannot reach different conclusions, and that you must interpret literally when told to do so, and symbolically/figuratively when told so.
Seems to me to be pretty cut-and-dried; the Catholic Church is - according to its own dogma - the sole arbiter of how to read and interpret scripture.
Now, about sola scriptura, I would merely point you to 2 Tim 3:14-17. Paul explicitly states that the scriptures written and lessons orally taught at the time Timothy was a child were all that were needed to gain the wisdom to be saved. Nothing more, nothing less.
I also know enough of Catholicism to realize that the Catholic Church does not address this section of scripture, probably for the very claim it makes. You do not need additional teachings or writings to gain salvation. In fact, I would recommend a reading through the entire chapter (2 Tim 3) through eyes not colored of any church or dogma, but as a clearly scriptural warning about how institutions and men are corruptible and corrupted.
You push too hard to "prove" that there is no freedom to let the Holy Spirit guide the Catholic believer into the light and truth of the scripture.
The hierarchs are totally correct in drawing the line at some points, for instance the doctrine of the trinity. This doctrine is established in scripture though not explicitly named. To intrep the scripture differently is anathema in the catholic church (lower case intended.) Although there many not be the same hierarchies in Protestant denominations, a set of doctrines and standard bearers exist and the doctrine of the trinity is similarly established and maintained.
I think that we both agree with the understanding that sola scriptura does not ignore Christian history and tradition when seeking to understand the Scripture.