The key to a 10HP run is honestly not to waste your turns. When you can end combat in one attack and have both Mario and his partner’s turn, use the extra turn to top off your HP/FP with Sweet Treat or Appeal to get the Star Power back. Also, know your Stylish Moves for extra Star Power. It fills up so fast that you can regularly toss out the quite OP Earth Tremor whenever you’re full on everything. No need to run around with full resources. I also like the Badges that randomly regenerate you and the defense increases are also very important.
Muto and Chono are retired wrestlers from Japan (the former being more famous in the West as The Great Muta). An in-game they also use their real names. Yakuza tends to have real people make cameo apperances, but most of them wouldn’t be well known outside of Japan. Some characters appearing in side quest feel like they would be based on real people based on the way they talk about being famous, but I wouldn’t know.
I’ve gotten so used to looking at the details that I didn’t even notice the blatant fire-in-the-tent.