Grazie ! My Italian is self-taught, self-teaching and self-to-be-taught,
ergo pretty baroque, I know it
è vs. e : arrrgh ! I knew it !
pas, non : it's all about translating 'not'. The usual translation is indeed 'pas', or 'ne ... pas' with a verb.
It is not bad : Ce n'est pas mauvais.
How is it ? Not bad. : Comment est-ce ? Pas mauvais.
'Non' is usually the translation of 'no' (as opposed to 'yes').
'Non' to translate 'not' and negate something other than a verb belongs to 'special cases', so to speak. I cannot think of a definite rule, I hope a few examples will help:
1- Lack of a negative adjective :
SSSS is an unusual, unconventional webcomic : SSSS est un webcomic inhabituel, non conventionnel. (no present dictionary knows 'inconventionnel', which would be a perfectly well-formed word, though. I may be accepted at some moment in the future)
2- Technical or philosophical language :
Le charabia : un exemple de non-langage - Gibberish, an example of non-language (expect 800 densely-written pages for a thorough explanation of this...)
3- Refined, litterary language: exactly what you wrote ! :-)