We don’t believe God extracts a punishment or suffering after we die to atone for unconfessed sins. We pray for the dead because it is a good and righteous thing to do. We don’t make any definitions about how those prayers are used by God. The current catechism only hints at the “punishment” effect, but traditionally your church has taught there is suffering involved.
Transubstantiation is not about “how God brings this about”; where on earth do you get these mistaken ideas? The philosophical terms are merely used to delineate the difference between what we see and what our faith teaches us. What is dogmatized is the real presence. By the way, in over reacting against the Catholic theology, there are no shortage of Orthodox apologists who are, in fact defining things, and are speaking more along the lines of consubstantiation.