Hi Toneee,
sad to say, but the content plugin supported until today not the mp3 tag. This works only in the component output.
So it is not possible to use it in a article.
About the english translation:
- in the last releases i must write it self. But my english is not the best.

- the description soll say, that the option must set to OFF - not to ON. But you can test it with both options settings. On some servers works it also with .htaccess protection.
I have seen your PM and i will your answer tomorrow. But any help is very welcome.