I don't know if you are taking feedback at this point.
But this is a wonderful effort that I think is missing an opportunity here. The Sega Genesis version doesn't have the same graphics as the original BUT they wisely improved upon flaws from the game and included expanded levels AND better bosses.
One drag of the game is that they simply give you that Gargoyle boss again AND again. So the Genesis game remixed other bosses that were crammed into the final level and even added a couple of surprises. Like the fake princess who turns into a giant spider monster which was clearly inspired by the movie "The Thing."
Please consider including those quality of life changes. Otherwise this really isn't all that special when compared to a mame rom that one can download and be done with, etc. etc.
If part of your goal is to make an arcade perfect post, then maybe have TWO modes like some games do. One could be called "Remix" or "Arrange" or "Special Mode" and the other could be called "Arcade".
Glad to see there is still work done on this.
Good luck!