I agree that what you say in your article concerning the Koranic refutation of a Trinity consisting of God, Jesus, and Mary (5:72-75), on the one hand, and of a purely biological or carnal understanding of Christ as God’s “Son” (112:4 passim), on the other, is in perfect accord with traditional Christian theology.
I’m not so sure, however, about your interpretation of the formula “Messiah, son of Mary” (Koran 5:17). For the Christian, the “Son of Mary” is most certainly divine. This is why the Virgin is called Theotokos (Mother of God), and not merely Christotokos (Mother of Christ = Messiah), the latter being the epithet preferred by the heretic Nestorius.
A Christian would therefore very readily subscribe to the formula which the Koran rejects in this ?ya, though he would doubtless express the second half of the verse in reverse. The Koranic text says, “They indeed have disbelieved who say: Lo! Allah is the Messiah, son of Mary.” A Christian, on the other hand, would profess instead, “They indeed have believed (and very rightly so) who say: Lo! The Messiah, son of Mary, is Allah (God).” The reversal underscores the fact, of course, that there is “more” to God than the Logos alone.
On the other hand, if one maintains as you do that in its Koranic context “the Messiah, son of Mary” is meant to apply only to the human nature of the Son—as does the root Christos in the Nestorian Christotokos—then you may be correct in thinking that the Koranic passages you cite are in opposition only to some heretical view and not to orthodox Christology, though the heresy in question, contrary to what you claim, would be neither Monophysitism nor Nestorianism.
The Monophysites taught that Christ has only one nature, the divine, and that He has no human dimension at all; hence they would never have said, as you imply, that “Christ’s humanity is divine”. Meanwhile, as I’ve already indicated, the Nestorians would have concurred with the Koran that Allah (God) is not “the Messiah, the son of Mary”, for Nestorius used the term “Christ/Messiah” in reference to the Son’s humanity alone, which he construed to be something hypostatically separate from His Divinity.