I'd suggest eating real food before and after the ride. That way you'll get more than just simple sugars. Save the expensive nutritionally limited sports food for riding.

It sounds like you could use some more electrolytes. I prefer to keep my electrolytes and calorie sources separate so I can adjust them individually. You need a lot more electrolytes when it's warmer, but your calorie consumption stays the same. I use endurolytes, and for long rides (5+ hours) one or two salt tablets.

Two hours is roughly right- I've seen people who ran out of gycogen well before that, and well-trained athletes can go longer.