Finished this earlier today. Here's my full thoughts: https://backloggd.com/u/Rodenbeard/review/4968975/
Hopefully they don't come off as too harsh. I really admire the attempt you've made here, but there's a sizeable amount of room for improvement if you ever tackle a PM hack, fangame, or really any game project in the future. I will be interested to see what you do from here on out, though.
I played it with Rosalie's Mupen GUI and had a mostly bug free experience. There were some slowdowns, some music issues, but only one major crash during the final boss (the starstorm). Only other big issues I can remember is the game softlocking on talking to the master with Chompy out. When Solin appeared to talk the game stopped and hung on that moment. Going back in with Solin on point from the beginning fixed it though. That, and the Chapter 2 shopkeeper is a little too close to the items- its possible to talk to them and buy the rightmost item at the same time, making the game lock up.