I haven't shown him susing any but I refered to two separate spells that should point you in the right direction.
As for who he dressed up as yes, it's an oc simply becuase I knew what i wanted but didn't know alot about any one who might have fit close to that.
Will Negi show up? I dunno but if enough people show interest in it then yes I'll definitely work him in.
Does Konoka know about the rebel/rogue group? I think she had known about them in canon, or at least since some time just before the show starts. She probably has no idea how serious they are though. I doubt her guardian, Setsuna, didn't know it, since it'd be stupid not to keep her appraised about something she needed to know about in regards to threats to her charge. She knew and would never have kept it from Konoka.
I'm not 100 percent sure what Asuna knows but assume every one else does.
As for the magic thing? Asuna has been shown, in MSN when they went back in time, to know Negi's father Nagi even though she doesn't currently remember her past past she's supposed to be like 27-32 in reality and a magic kingdom princess. All signs point to the fact that yes she has always known about Magic. The real question is has she repressed it? Near the end of of MSN, like in the 20's episode wise, she says something like so it really happened in response to a dream about the demon she made that deal with shortly before her birthday party. I'm going to say if she's been suppressing it then she's probably been ignoring any magic she has seen.
As for Konoka and magic I think that she had been going to meetings for her father or grandfather's magic associations for part of the last year before the show starts. Here the answer is yes she knows about magic, after all she's surrounded by wizards and her family is full of them. I doubt that it's possible for them to keep it quiet from her simply because of the sheer volume of it around her.
Group dynamics are not always going to be nice and friendly since at least a couple of them are going to clash but those should show themselves rather quickly. I won't say who now but it should show itself next chapter or the one after that depending upon how long it takes me to recap what was going on durning those three or four days at Hinata sou that you weren't shown.
Edit: Stuid kids hitting the enter button with their elbows.