“You are speculating about what may or may not have transpired within the confessional and the heart of a priest in a hypothetical case.”
Yes, only in a hypothetical case, and in the general sense, and not about any person in particular, so there is nothing forbidden about that.
“However, the relative sinfulness of the priest is not sufficient to prevent Christ from acting through him.”
Then there is nothing preventing Christ from acting through a heretical priest, who is in the same position, being in de facto excommunication. Yet nobody seems to suggest that it would be efficacious to seek absolution from them.
The Catholic church does teach that defrocked priests can administer sacraments in an emergency, but only with the caveat that it should only be done in a situation of the direst need, where there is no alternative. Obviously, this caveat means that seeking the sacraments from such a source is not the most efficacious method, even if you hold it possible for sacraments thus administered to be valid.
Yet, a defrocked priest is still in communion with the church, even if they have stumbled in their calling. A unrepentant sinner, priest or no, is not in communion with the church, so it stands to reason that seeking the sacraments from them would be even less efficacious, and therefore less advisable.
Your argument reveals a significant misunderstanding of Catholic teaching. The sacraments are efficacacious, not because of the holiness of the priest, but because it is Christ himself who acts through him. I have offered several times now to let you know what the teaching of the Church is, not so that you come to accept and believe it, but so that you can at lease intelligently express and argue the facts
Peace be with you