I just finished the 5th season of HxH and there are somethings i don't get. So will share my opnions in this battle anyway.
Round 1 Meruem Pre-Nuke vs Gon-san.
Round 2. Meruem Post-Nuke vs Gon San.
My opnion on this battle: Gon San wins, booth rounds. Round 2 with extremely difficult (could loose if not careful enough.) Why?
-Was able to dodge with no effort pitou atacks.
-Judging by his face, he was able to effortelsy fatally wound pitou with a regular kick.
-Meruem tried to kill Pitou before with a strong attack with intention to kill her. She barely felt it.
-It seems that he wanted to loose his arm for whatever reason. He easily dodge the same atack again. Killua also noticed pitou atacking him. Judging by his previous feats in the same form, there's little doubt he was also seeing this atack.
-Was so fast that it was able to escape from pitou sight. She was able to feel netero flying up in the clouds. She's also extremely fast. There's no reason to belive Gon completely outmatched her in speed.
-The full extension of jojokenpo power is unknown. Judging by his face again, Killua stopped Gon from releasing a full powerd jojokenpo, or either he wasn't using the full extension of his powers. Hited as hard as the nuke anyway.