After all those helpful examples, I hate to be the bearer of yet another message, but I'm not sure anyone has really said this clearly enough yet.
You seem to have forgotten that the preposition 'von' always takes the dative. You know that because it's one of the list of eight that you can sing to the tune of the 'Blue Danube':
Aus, außer, bei, mit,
nach, seit, von, zu,
aus, außer, bei, mit,
nach, seit, von, zu ...
https://resources.german.lsa.umich.edu/gramma...There's no way around memorizing that list. Then the question of how to form the dative of an adjective serving as a neuter noun becomes something you can find in a grammar lesson with sample declensions:
etwas / nichts Gutes
für etwas / nichts Gutes
zu etwas / nichts Gutem
In masculine and neuter, that M has to show in the dative. If there's not a der-word or an ein-word to carry it, like 'dem' or 'einem,' it falls back to the next declinable thing, which is the adjective itself.
If you already understood all that, sorry, but just in case. (-: