Music track and lyrics

Can I put lyrics on a music track to be part of a featured film, short film, fictional-drama video? Can I sell DVDs of this movies containing these “song” as a part of the footage?

What happen if the public, then, like the “song” and I want to sell these new song based on the audiojungle item? I can’t do it at all or is there any special license for that?

You need to redeem the track from the author and so that he removes it from sale here (if he goes to your deal). The track can not be inserted into your song, this means a complete buyout of copyright to music, which is prohibited here (Envato, AudioJungle).
To negotiate with the author!
Good luck!