Is there any extant pre-Schism (i.e. Before 1054 AD, when the Eastern and Western chueches anathematized each other) commentary on the golden calf incident of Exodus 32:1--6, and if so, where?
The Ante-Nicene Fathers (ANF) volumes are all freely available online, along with many other Patristics. I got over 300 hits with a search for "golden calf." and found several notable quotes. Keep in mind that the Fathers often allegorized/spiritualized scripture while discussing living for/in Christ. You can also study the passage and select works that reference it.
During the Roman period and long after, the golden calf episode was a source of embarrassment to the Jews in their relations with the increasingly aggressive Church, which fully exploited the story in its polemics with the Synagogue. Even Josephus, who was concerned only with pagan antisemitism, was evidently afraid that the biblical account might be employed by Alexandrian antisemites to lend credence to their allegation that the Jews worshiped an ass's head in the Temple (cf. Apion 2:80, 114, 120; Tacitus, Histories 5:4). Josephus accordingly omits the entire golden calf episode from his account of the Israelite migrations in the desert. Instead, he graphically depicts the deep anxiety of the Israelites concerning Moses and their joy when at last he came down from Mount Sinai (Ant. 3:95–99). Not only did Moses not break the tablets, but he actually displayed them to the rejoicing people (3:101–2). Josephus also omits any reference to Aaron, and the same is true of Philo who does not, however, completely suppress the golden calf narrative (Mos. 2:161–74, 271).
As early as the immediate post-crucifixion era, Stephen, the first Christian martyr, sharply denounced the Jews (but not Aaron who was held in veneration by the Church) for having made the golden calf, which became the fountain-head of Jewish crimes throughout their history, culminating in the crucifixion of Jesus (Acts 7:41–52). For the Church the golden calf episode served as proof that the divine covenant with Israel had never been consummated, so that the Jewish claim to a special relationship with the Almighty was unacceptable (see Smolar in bibl., p. 91). By worshiping the golden calf, the Jews had revealed their foolish, stubborn, unrepentant, and immoral character (ibid., 100). Augustine also associated the calf cult with the worship of the devil, and the Jews who had drunk the water into which the powder of the golden calf had been cast with the body of the devil (ibid., 100–1). The medieval identification of the Jew with the devil was no doubt influenced by this extreme patristic interpretation (ibid., 101, n. 12). Source
You might also find this article interesting. I apologize for the hurried and scattered response, I am very busy this evening but wanted to point you in the right direction.