Deuteronomy 32:8 in 4QDeut-j reads “sons of God” where the Masoretic Text reads “sons of Israel.” That’s a theological change in the transmitted text, not a spelling slip.

Yes, and it is one of the best-known substantive variants, where the Scrolls and the Septuagint preserve the older reading and the Masoretic scribes apparently altered it. Modern translations such as the ESV now follow the Scrolls here. This is textual criticism doing its job in public: the difference is visible, can be studied, and has been corrected in the Bibles people read. A hidden corruption would leave no such trail. Faithful transmission includes preserving the evidence of where the text once differed.