It's a longish text without a specific question and writing forum isn't the hottest area around here as for most the professional interest is in coding, so don't take it personally
The story is great and you have laid the foundations to start building visual assets for your game. But don't nail anything totally down because you could be developing this for months and look how much progress you've made with the story in just a week
When I read stories I also visualize it and think about all the assets you need for it. I think there's a lot you need to make just for the cutscenes and that can be considered a good investment in story giving more meaning to your game. Since you have artistic talent I don't think making them will be an issue at all. And maybe you can re-use the misc background props in your level design as well. I think you'll want to schedule things so that are developing the game levels along with intro so that things don't get too monotonous for you and you don't totally forget either of them. Target releasing the intro along with the first chapter of your gameplay and you're off to a good start that should provoke much more interest than just "a platformer game".