To solve CSS being added as a content of the document, please install and enable Tidy for PHP. About this issue please check the information available on:
There's a warning about this issue. We recommend you to install enable mbstring extension too, to work with all characters.
About your other problem, it's strange, because you are getting a denied access but it you have set 777 access to that file it should load the file. Please check that you have set the isFile option as true of the embedHTML method.