"metathesis" would be more accurate for change from "God" to "dog"

A change in a word, for example by adding, omitting, inverting, or transposing its letters, syllables, or sounds.

From which it would seem that metathesis is one form of metaplasm. The use of gone for damn(ed) would follow from the replacement of the d at the end of God with the g of dog thus suggesting the d of damn(ed) be replaced with a d. But *gamn(ed) isn[t a word, so the word gone is used instead. Metaplasm at three different points in one two-word phrase.