Thank you for thoughtful post. Even if Paul V1 Was head faking, the continuity of teaching is present in the Encyclical. Remember the future JPII was present at the Council and the heroic intervention of Ford and Grisez at the BC Commission were both Providential.
The big issue is the confusion in the Church caused by the use of the word mortal sin and the deformation of the concept of conscience, neitherc ever remedied.
BTW. I had a dear Jesuit friend present at Councul and BC commission. He worked tirelessly to promote H.V.
If I’m understanding you correctly, perhaps we just simply disagree on the role of the Catholic Church. I do not believe for a moment that the Catholic Church confuses anyone with the term “mortal sin”.
But what has confused a great many Catholics, and in my view is largely responsible for the unchecked immorality sweeping across the world, is the Protestant concept of “let your conscience be your guide” that you are suggesting. Unlike the worldly-influenced subjective beliefs of the conscience, mortal sin is a well-defined objective standard that has faithfully guide for millenniums.