I don't know much about your specific tablet, but I'll ask this anyway: have you bothered to toggle the option to allow apps from unknown sources? Also, what ROM are you running on your tablet? That could also play into it, as I've used custom ROMs in the past that specifically wouldn't run that app.
Doesn't matter. Just because you managed to load it is no guarantee that it'll run. Second, you'd have to "hack" the app, or run custom firmware for it to work with a front-facing camara. It's your time and effort to expand, bit for me it wouldn't be worth it.
Then I tip my hat to you for finding a way. That being said, both my experience with a tablet that lacks a rear facing camera, plus things I've read about it (see the review of the N7 by the Verge to see how they also couldn't find most camera apps to work with it either) lead me to conclude what I did. And I still see no reason to believe that the apps in question *aren't * looking for a rear camera. If they weren't, you would have had an easier time loading and running it.