Even more theory/spoilers
I definately think that you're right again. Chris is definately not as air-headed as we think he is. I forgot about the fact (and didn't fully realize at the time) that he picked up on what Russel was doing without it ever being hinted at/mentioned. I also feel like Zach might have known Russel when they were younger (like you said). The car scene when they "first" meet with Zach already knowing/recognizing Russel's name and hugging Russel and acting comfortable with him, which is completely out of character for Zach, helps point to/support the theory that they have some kind of history that we don't know about. This would explain why Zach thinks Russel is innocent (like you said). Zach's connection to the "red hood" is interesing. I think that Zach might have some knid of personal connection to them in some way based off of how invested he is in them and how much he knows about them and their murders. Maybe he could have possibly known or been related to one or more of the "red hood's" victims. Or he might even know/be related to the "red hood", but that one is a bit of a stretch.
All in all, theorizing about all of this just makes me even more excited for the next public update. Hopefully it will help answer/give more evidence that can point us to more clear answers for our questions/theories and not just leave us with more questions (even though that wouldn't be too bad if it did, just more to theorize about).