I talked with Dansup about group implementation in Pixelfed last November, but didnt hear anything new since then. Based on that, there doesnt seem to be much progress (though I might have missed things as I dont follow the development actively).
as I outlined earlier, aiming for compatibility with ActivityPub implementations that do not have a specific concept of groups is a double-edged sword: this means it’s hard to distinguish a provide a consistent UX for groups (e.g. people complaining about everything from a group being boosted in their timeline) especially with other projects (such as Peertube) using
Groupactors to mean a different thing
I am actually considering to specify the group in as:audience field in the future, as discussed in [this thread}(Unresolved issues surrounding Follow activities - #20 by nutomic). This seems much cleaner as it doesnt rely on extracting the group from cc field. It should also solve your first and third point (not sure about the second).