⟨ñ⟩ for /ŋ/! That’s a fun way to handle it. I also see you got ⟨ĥ⟩ from Esperanto, and swapped the diaeresis with umlaut.

There’s also ⟨Ħ ħ⟩, Maltese style. I often use it for /h/, when I don’t want H-digraphs to interfere.

Those rules for ⟨c⟩/⟨ç⟩ vs. ⟨s⟩ hint some etymological reason, like older /k/→[…]→/s/, Romance style. It’s messy but the good kind of. And your example with ⟨garço⟩ made me notice your conlang got some French vibes, I like it.

On the vowels: the diacritics became a bit of a mess, I think your first revision with digraphs+diaeresis was better. Personally I’d go with something like

/i y u/ ⟨i u ou⟩
/e ø o/ ⟨ie eu o⟩
/ɛ œ ɔ/ ⟨ea oe oa⟩
/ɑ ə/   ⟨a e⟩

And then diaeresis on the second letter to ensure separated reading, and/or acute on the first for disambiguation.

So /xafɛ/ ends as ⟨ĥafea⟩ “wheat” and ⟨ĥaféa⟩ “café”, and your little abomination is ⟨ĥñoeññngoiëche⟩. (Note: most languages would quickly convert that /ŋŋng/ into /ŋg/, so your word would end as ⟨ĥñoeñgoiëche⟩.

I’m just throwing ideas, mind you.