I know that the Haydock commentary says that it should be understood as sin offering in 2Cor 5:21, but I am not familiar with a magisterial source for this. Do you know of one? If it is merely a theological tradition, it would not be heterodox to take it as meaning sin.
The statement was in the context of a meditation on the typology of the bronze serpent. As a type, the serpent represents Jesus. But in other places serpents represent the devil. Francis meditates on the mystery of the Cross to consider how these seemingly opposite symbols coexist. Within this imagery, Jesus removing our sin by being "lifted up" (the expression in Scripture) is like Him becoming a devil/serpent. It is not a claim that Our Lord was a devil in the sense of saying that Our Lord was evil.
I'm just not seeing an outrageous blasphemy in either the words you quoted or the ones that I did. I can see that it might be confusing without the context that he was talking about typology, but I cannot understand how there is a problem in context. It all seems to be leading to the conclusion that the only true salvation is in Christ crucified. That idea is certainly orthodox.
The only "context" in which "Jesus became the devil" is defensible is the context of quoting the blasphemy to damn it.
There is no "meditation" or "typology" that excuses "Jesus became the devil."
The sinlessness of Jesus is affirmed in these verses: 1 Peter 2:22, 2 Corinthians 5:21, Hebrews 4:15, 1 John 3:5, John 19:4, John 8:29, 1 Peter 1:18-19.
Until Jorge there has never been a need for the Magisterium to explain that sinless Jesus could never be the devil.
It is a sad state of affairs that there is even one "trad" here who thinks a "meditation" or "typology" or "context" canonizes such a blasphemy as Magisterial orthodoxy.