Nom, the gemara in Sanhedrin uses the term ruach hakodesh as well, but it is clearly referring to nevuah, because of the juxtaposition with chaggai zecharya and malachi, who were neviim.
Ruach hakodesh itself was not batul, as the divrei chaim wrote in the teshuva you quoted, so much so that to doubt that gedolei yisroel have ruach hakodesh in every generation is apikorsus, the divrei chaim said.
Nevuah is ko amar Hashem. The words of Hashem communicated to a person. Ruach hakodesh is either what Hashem puts into your head, or being mechaven to the emes in learning.
Your sources have basically no bearing on nevuah – the rishonim on Sanhedrin clearly identify ruach hakodesh as referring to nevuah; this should go without saying.
The gemara also says that once nevuah was lost it was given to katanim and shotim – another proof that it is gone. Bava basra 12a, statement from rebbe yochanan “nevuah was TAKEN from the neviim and given to katanim and shotim”
I forgot to mention that gemara too.
Again – let’s find one case where a tanna, amora, rishon, or acharon calls someone a bonafide navi. You won’t.