I agree with you on the balance issue. It may or may not apply to the specifics of the choke you were using, but what I think is effective is to get the bottom guy focused on the choke, switch to side control and clock around to finish. That tactic really works well when the guy tries the knee to elbow escape. As soon as he goes for it, just give up the mount, go to side control on the other side and try to finish from there. I got smoked on the bottom so many times that way when I first started at the gym I train at now. I had a pretty good knee to elbow, but they were always ready for it; they just gave up the mount and got a really tight side control which was as good or better for them than the mount. I realize now that's a pretty basic technique, but I'd never really seen it.
If my hands are in his gi for the choke when I'm on top, the best way I can defend the bridge and roll escape is to sort of ride up with the guy. Usually, when you give him that much space, he'll try the knee to elbow, and I'm ready to just give up the mount and move to side control.
All that probably means, though, is that I need more work on my top mount game.
Open Mat in 48 minutes. Yee-hah! Time to start taping all my injuries.