Should be "backs" because long-s isn't used if it's the end of the word.
> Before a hyphen at the end of the line a long ſ must always be used, for example Shaftſ-bury.
The hyphen is not at the end of the line. Shaftſ-
bury is just Shaftſbury with a hyphenated line break.
That's when hyphenating a word, not between different words linked by hyphens.
That's exactly what a hyphenated word is.
No. "Hyphenating a word" here means when a whole word is split by a hyphen to continue on the next line of a justified column of text. In that case only, a long s is used before the hyphen.
The example of "Paradise loft" written as "Paradife loft" reminds me of the Norwegian newspaper Aftenposten's logo looks like Aftenpoften