Hmm. Seems like you'd be walking a fine line here no matter what you decide to do.
Well, I'm all in favor of learning a little bit more about non-story characters, or at any rate characters who haven't shown up recently (like Taye and Forrest). I really liked it when you gave Calin and Marta personalized LTWs -- you could share those for all the characters, story and non-story alike, and hopefully it won't give too much away.
I agree that the stats for the vampires and werewolves might be a bit harder to pull off without giving stuff away. Hmm ... you know, if it were me, I might decide to write up clan statistics (because your vampires operate according to clan, no?), with typical clan weaknesses and strengths, and notes on how aging affects these weaknesses and strengths. So we might get an idea of what Siren's powers are (and why she isn't to blame for everything that goes wrong in Grimstead, apparently!
), but we won't know anything too specific.
And Risa, as far as I can tell, doesn't seem to belong to a clan at all, so we wouldn't have any idea what her powers are!
I also agree that it's way too soon to reveal how Abel feels about Persia or his brothers (though I think, personally, that his animosity against Peter is nothing more or less than a sign of intelligence and good taste!
) But surely there are other things you could reveal ... such as, what was his relationship with his father (or his mother) like? Where was Abel, and what was he doing, when he found out his father had been killed, and how did he react to it? I guess it's a little bit like those 10 things lists -- pick something that won't give away too much for your story, but that might give readers an insight into the character.
And of course, lastly there's the good old spoiler warning. You could even color the text the same color as the backround, so if anyone wanted to read it, they would have to highlight the text. Then you can't say you didn't warn them!