Deary Jansy
What you call the "first limerick" doesn't make sense without the second, so I think they are both the work of MRK, who, being a monsignor, was very Catholic, and being very Catholic, was very anti-atheism, which of course is part of the force of the limerick ...
Now, as to V. Cantaboff - just thinking - devious VN may have used the additional misdirection of using latinate letters to hide cyrillic ones. So the C of Cantaboff may be an S and the n may be an h. That would make the letters to unscramble (listing consonants first) V, S, H, (or SH?) T (or TS?) B FF (aka V) and the vowels a, a, and o.