Deuce,
I'm at my 4 month post concussion this week and I too feel like I am at a standstill. I'm not getting better and I'm not getting worse. Very frustrating.
From what my physical therapist has told me and from what I've read, light cardio is actually good for you. If you feel dizzy or any pressure, of course, stop but I do @ 20-30 min easy cardio and I think it oxygenates the brain.
That of course is nothing like the workouts I was used to pre-concussion but at least it's something.
I agree with Mark, reducing stress is very important and as far as alcohol, I agree, it's a toxin and I would say not even one drink until fully recovered.
Good luck!