I'll check DQ3 tomorrow night, unfortunately won't have access to a PC until then.
I posted over on gbatemp form some help. They seem to be pretty knowledgeable, but from what they said it looks like its not possible.
It looks like they're saying you might have to use another emulator.
I don't know if it's related to the patch, but it's the first time ever that I ran into this glitch. While fighting the arena in chapter 5 with a Brave Sword, Dew somehow kept fighting even though his HP reached zero. This didn't happen with any other weapon.
Here's a video of it:
Also included is my save file, load the fourth save slot and have Dew fight the current arena match with the Brave Sword and you should be able to reproduce the glitch. This happened while using the fourth beta.
I spent today looking into this issue, and I think I see what's happening.
The game copies Dew's HP and stats to a separate area of RAM for visual calculation. But whenever he takes a hit or heals himself with Sol, it's also trying to keep his original HP up to date. The problem happens when Sol procs on a Brave sword hit. Sol is only healing for the first hit in the arena, but the game thinks it should be healing him twice and updating his original HP.
So when he takes his first hit, he goes from 41 HP to 19 HP. Then on his next turn, he activates Sol and heals himself for 5 HP, going up to 24 HP. But the game thinks he should heal twice, and updated his original HP to 29. This continues until the "deathblow", where the arena visuals show him at 12 HP, but the game thinks he has 27 HP. So Nazarre's last hit deals 22 HP of damage, making it appear that he should die. But the game actually says Dew has 5 HP left now.
TLDR: Sol and Brave swords break the arena. I can fix it so the two HP values stay consistent.