I've heard almost as many confessions as I've done funerals. It's not a weekly or even monthly occurrence, but I wouldn't say it's rare.
I think the language referring to the topics discussed during confession not normally being a topic for subsequent conversation is clearly linked with the pronouncement "the Lord has put away all your sins..." The new start offered by the Reconciliation of a Penitent means that one can put ones sins behind them. Confession frees us from the past in order to live toward God in the present and future. If these things are brought up again, they should be brought up by the penitent; the confessor is to be a symbol of God's grace filled forgetfulness unless the penitent's conscience remains troubled, and then it is they, and not the confessor, who broaches the topic.
The statement about the secrecy of confession regards another issue, namely, the discussion of the content of someone's confession by the confessor with a third party, which is forbidden.
I believe the majority of the texts you cite from the English reformers are attacks upon auricular private confession as a dominical sacrament, i.e. normally required of every person for salvation. Of course, Anglicans deny this. That does not mean that auricular confession was outlawed or not practiced. Nor does it deny its sacramental character for those who choose to engage in it. Historically speaking there is evidence to show that those who wanted used the means of the private confession in the ministry to the sick to accomplish this purpose. It was deemed appropriate since sin is indeed a sickness, for which the gospel is the cure--and the pronouncement of forgiveness of sins is at the heart of the gospel.
I would also commend a study of the words of the Exhortation before Communion, found in every prayer book since 1549. The 1662 ends with these words: "And because it is requisite, that no man should come to the holy Communion, but with full trust in God's mercy, and with a quiet conscience; therefore if there by any of you, who by this means cannot quiet his own conscience herein, but requireth further comfort and counsel; let him come to me, or to some other discreet and learned Minister of God's Word, and open his grief: that by the ministry of God's holy Word he may receive the benefit of Absolution, together with ghostly counsel and advice, to the quieting of his conscience, and avoiding of all scruple and doubtfulness."
There's little doubt that this describes the practice of individual auricular confession with absolution pronounced by ordained Ministers of the Gospel.
Since it's apropos of the article, I'll also share that the issue of whether, in an extreme situation, one would break the seal, came up in several of my seminary classes. You'll be interested, I'm sure, to know that Mother Julia Gatta, who teaches pastoral care at Sewanee, teaches in line with the prayer book rubric, that the seal of confession is absolute (I heartily recommend the book on confession she co-wrote with Martin Smith, "Go in Peace: The Art of Hearing Confessions").
The likelihood of ever having someone confess a crime that must be reported seems low. If that did happen, I think there are several possible responses: making the person turn themselves in as a prerequisite for absolution, including the possibility of physically accompanying/escorting them to the authorities (something I have done once, though not out of the context of the rite of reconciliation, but rather a general counseling session). Finally, if I were convinced that someone were in immanent danger and the only way I could prevent it would be to break the seal if the confessional, then I would, and the next thing I would do is to resign my orders for having broken my ordination vows. Thankfully, that last scenario is about as likely as most abstract ethics problems--the man on the train tracks etc... (I should note that I owe the extreme solution to my mentor the late Rev. Dr. Guy F. Lytle. We discussed this issue in his class on the Priesthood).
You make that statement, which I've often heard expressed by those of a particular ideology, which claims that the rubrics of the BCP have the force of canon law, and that a breach of the rubrics constitute a breach of one's ordination vows. Can you document that in the canons? It has always struck me as an implausible interpretation of the role of the BCP. I see how conservatives would like to sustain that claim in order to hold the view that inconvenient acts of General Convention are not binding unless we revise the BCP, but I've always seen that as a specious argument.
By the logic of your claim, a priest breaches her ordination vows by omitting a step in the liturgy or kneeling /standing when not specifically authorized, or not doing celebrating a commemoration according to the calendar or not preaching from the RCL. I am aware that some do have such a legalistic approach to the liturgy, but I am unaware that such an interpretive stance is warranted by our canons. Can you point me to the canonical basis of your claim that not following the rubrics of the BCP constitutes a breach of one's ordination vows warranting resignation from the order of presbyters in the one, holy, catholic, and apostolic church? Is it all such failures to follow the rubric, or is there an established hierarchy of categories of rubrical defects, or is there a subjective prioritization of such rubrics that you presuppose?