Wow, I am very grateful, I did not think to receive such a complete review, all this really will be of great help to me. I will have to divide my answer in parts:
The concept of the game: I'm trying to do something different but using the classic style jrpg. I agree with you that the name of the game could be better. My plan for the magic cavern is to be an epic journey to unknown worlds, like the chickens town (yes, that's the level name) I want the levels to be unpredictable and unique. After the jam I will begin to work pretty hard so that the complete game has that essence, the spark of "what will happen next?".
The humor: I didn't expect that this will be notable in the game, a lot of the jokes were not designed in the plot, sometimes I add them to joke about the mistakes in the game. But now I know that several people liked it. I will use that in the full version.
Characters are a bit shallow: Yeah, you're right. The characters and their dialogues is something that I have to improve, I didn't design them to focus on a younger audience, but to shorten the development time a bit, that's why in the final scene I joked about this. I am the type of player who values the deep and human characters in video games.
The name of the game and the marketing: Thank you so much, it really is as you say, the name of the game does not give the impression of what the game really is. I will also work on the title, details like that are what make a player choose the game in the midst of millions of other options.
The beginning of the narrative: Is not necessary need to tell the story of Nate's father at the beginning. That's a good advice. The important thing at the beginning is to know the reasons why the protagonist goes to the cave, not the reasons of why his father went. Actually, the story can more interactive. As the game progress, the story unfolds. I will work on it.
Game mechanics and battle style: For now the game has the classic battle style (the only one that could be implemented quickly), but in the future version that will change. The random battles are not very fun (my own experience) it's much better to see the enemy and choose to fight with him or runaway. I will take into account your recommendations of mario rpg (very good game, I played it a long time ago, but in that time my level of english was really low and I could'nt finish it), paper mario and Bravely Default (I haven't play it, they seems really interesting). I have not yet defined how the system dynamics will turn out, but these games will be useful for me.
Level design errors: I will take into account those places where you got stuck. It's true that exploring helps to give more depth to the game, but it's better if it is explored through small clues, at least when it is the first time that the test or riddle is shown.
Forgive me por la edición spanglish (XD): the first version of the game that was uploaded was full with translation errors (even I got lost in the dialogues), then I uploaded a version with a better translation, but many like players had downloaded it.
I appreciate the time you have spent to give me this amazing review. Each element (pro or con) will help me a lot.