I’m afraid it’s a serious mistake to write, as you have, that “most Christian theologians have labeled the belief in one fully Divine Jesus as the monophysite heresy”. This is by no means the case. Every orthodox Christian believes and teaches that there is only “one” Jesus and that He is “fully divine”. Monophysitism is the heresy that claims, not that Christ was fully divine, but that He was only divine—that His divinity was such as to overwhelm or destroy His humanity, with the result that after the union effected by the Incarnation the only thing “left” was the nature of God. The Church rejected this claim—at the Fourth of the Ecumenical Councils (Chalcedon, 451)—on the grounds that divinity and humanity are not related in the same way as physical objects, which cannot occupy the same space at the same time. On the contrary, human nature becomes all the more perfectly or fully human when it’s joined with the very nature of God. Insisting on the “two natures” of Christ is therefore a crucial step in safeguarding the soteriological heart of the Christian tradition, as this is expressed in the well-known Patristic maxim: “God became man that man might become God.” Only if divinity itself is fully human can humanity be fully divine.