So let me get this straight. When Theodore states the The Word of God is one person and that the Christ is another person, making two different persons, is that what you confess also? This is clearly contradictory to Scripture over & over again. 'Jesus Christ is the same yesterday & today & forever. He is one Person with two different natures, the Divine & the human. It is all the heretical beliefs that teach contrary to this historical Christian doctrine.
The problem with the condemnation of Theodore is that assumes he was using language standardized at Chalcedon. But he died before Chalcedon. The most recent council was Nicea. Before Chalcedon “hypostasis” and “ousia” were sometimes almost synonyms. In the initial Nicene Creed, we see the following condemnation”
“But those who say: 'There was a time when he was not;' and 'He was not before he was made;' and 'He was made out of nothing,' or 'He is of another substance' or 'essence,' or 'The Son of God is created,' or 'changeable,' or 'alterable'— they are condemned by the holy catholic and apostolic Church”
In Greek the phrase “substance or essence” is ὑποστάσεως ἢ οὐσίας. Nicea saw them as virtual synonyms. I doubt you'd want to condemn the authors of the Nicene Creed for confusing hypostasis and ousia.
Theodore believed in the unity of the Son, but he didn’t use the term hypostasis for it. He typically used “prosopon,” although his language wasn’t entirely consistent.
He associated the hypostasis with the nature, which was appropriate at the time. What he seems to have meant (and I’m depending upon secondary sources here — I’m not an expert in his work) is that the Son didn’t assume human nature in the abstract, but an actual, specific, body, mind, etc.
Aquinas makes the same point in the Summa: “The Word of God "did not assume human nature in general, but 'in atomo'"—that is, in an individual” Indeed Aquinas, as is common in the West, treated the human nature as almost a pseudo-hypostasis: “Therefore, although this human nature is a kind of individual in the genus of substance, it has not its own personality, because it does not exist separately, but in something more perfect, viz. in the Person of the Word.” As I read it, the human nature was just like a person, except that we don’t call it a person because it’s part of something larger. Indeed I think "individual" is a reasonable translation of hypostasis.
Before Chalcedon, Cyril also used language that after it could easily look heretical. But he accepted Chalcedon, and his intent was understood as being orthodox. Theodore, of course, didn’t have the chance to accept Chalcedon, nor to use its clarified wording. Many people writing before Nicea or Chalcedon said things that on the face of it weren't entirely consistent with those creeds, but we interpret them generously unless there's much better evidence of heretical intent than is present for Theodore.