Question on using public domain materials

[breakaway]

1) Do I have to legally mention anywhere that I am using it?
2) If I edit a public domain video by cutting scenes, and adding some of my own, does that make me the copyright owner of this version of the video? (obviously I wouldn't be able to stop people from copying the public domain elements, but my new presentation of it, and also the new scenes/characters I add are what I'm referring to)

 

[The Occultist]

You do not have to provide notification that a work is copyright to you, but it's not a bad idea.

Yes, everything you create artistically is copyright to you, as long as you realize, as you already pointed out, that the public domain portions of your work are not part of your copyright.