As cool as a level editor would be, I think right now it would delay the development of the main game too much. Maybe it will happen some day, but I can't promise that, tbh.
In the menu under "feedback" there is a link to a feedback-form. All fields are optional and at the end is a text field. Feel free to submit your ideas that way.
As for the soundtrack, credit where credit is due: lo-fi ost