Page 182. " 'Credo in unum Satanum,' "

Translated from the Latin, this means 'I believe in one Satan'.

A credo is a statement of Christian faith, 'Credo in unum Deum', meaning 'I believe in one God' is the first line of the Nicene Creed, which was written in the 4th century and recited during religious services.

Page 183. " 'I wanted to be in a state of Grace when I married you.' "
Praying hands
Creative Commons AttributionPraying hands - Credit: Jenniferschwalm
A state of grace means to have recieved the sanctification of God. Rose is most likely to have aimed to achieve this by the purgative way, by obtaining justification but still struggling daily with temptations that she has not yet learned to control.
Page 184. " 'Roses, roses all the way, and never a sprig of yew.' "

Requiescat (meaning 'rest in peace') is a poem by Matthew Arnold written in 1853.

Strew on her roses, roses,

And never a spray of yew!

In quiet she reposes;

Ah, would that I did too!

Mr Prewitt confuses Requiescat with The Patriot by Robert Browning, another Victorian poet with whom Arnold was often compared.

Yew trees are often planted in church yards, and can be seen as a symbol of sorrow or death. Sprays are sometimes placed on coffins to symbolise resurrection and eternal life.

Page 194. " he'd got her like you got God in the Eucharist - in the guts. "

Eucharist
Creative Commons AttributionEucharist - Credit: paukrus
The Eucharist or Holy Communion, is a Christian sacrament derived from the Last Supper, during which worshippers receive consecrated bread and wine which symbolise the body and blood of Jesus Christ.

'Take, eat, this is my body... Take, drink, this is my blood... Do this in remembrance of me.'

Page 200. " 'You'd hang,' the Boy said "
Gallows
Creative Commons AttributionGallows - Credit: Pretzelpaws

The minimum age for hanging in Britain was raised from 16 to 18 in 1933, under the Children and Young Person's Act. Aged 17, Pinky would escape the death penalty for murder.

Capital punishment for murder was suspended in the UK by the 1965 Act, and abolished in 1969.