Hey Will, how long did you try to stick it out with the low carb diets? Perhaps you got to the "withdrawal" state but never fully adapted?
When I went full on paleo, my only high carb source was sweet potatoes or yams post workout. Otherwise it was fruits and vegetables and relatively low carb. Not ketogenic low, but probably less than 50g carbs a day, not counting the post workout tubers. I found that macademia nuts made the transition much easier.
As I'm sure you read in Robb's book, we don't actually need carbs at all. Your body can create it's own glucose, though it is not necessarily an efficient process. I think if you can slowly decrease your carb intake, the transition may go smoother. In fact, if you're really motivated, you could try the zone diet with paleo foods. You'll find it's easier with alot of fruit which is not necessarily optimal because of the fructose, but at least it would get you away from the grains, and help your body with the transition.