1. I think I get it even though I never played DMC and the only Mario I am familiar with is the first one. It's good that me pointing it out helped you notice you did not explain in in the game. The game is surely become clearer the more you flesh it out.
2. I think maybe instead of halos an icon showing state above enemies would be better, but I did not play with halos enabled, so I am not sure. I imagine if people prefer to have less immersion breaking UI, they would prefer halos.
3. Yes, it definitely needs to be in different section.
4. any orb health indication is better that none, so make sure you add it for next DD.
5. Trust me, I get it.
As for the "Fun" part of the game, right now it's just funny how much the animations are broken and of course the wet sounds. I think you're going to need to flesh out the game more for me to see if the actual gameplay is that much fun, but bear in my I don't play games like this. I am happy I can help.