As far as angel aggression goes that is just figuring out a little pecking order. I would move that floating breeding trap out f the corner, make it so it is mode centered in the tank. This will provide more of a natural divider. You also need some taller decorations in there, you need to break up that long line of sight.
If that larger half black is being really aggressive the smaller marble will be pinned in a corner, or trying to hide horizontal at the surface. While the marble is showing some submissive behavior, it is remaining vertical, meaning it is holding its own. While the half black is making some half hearted charges, it is not starting the charge at an angle, which is a typical aggressive stance with cichlids.
That marble looks big enough to hold its own against livebearers, the half black certainly is. I would worry more about the swords, who with the long tail look similar to an angel, getting torn up. Livebearers are no where near the aggression level of cichlids.
I watch angels behave this way all day long, until you start to see any tearing of fins there is really nothing to worry about. Being the weekend you have time to keep an eye out for this.