If you're trying to gain muscle, you do need more carbs than 20-30% of your diet. Carbs convert to glycogen, which is your muscles' preferred form of energy. To get the most out of your training (and therefore muscle growth), your muscles need carbs to function at their optimum. Just stick to the complex (like oatmeal, sweet potatoes, brown rice, etc.) and fibrous (veggies like spinach, broccoli, etc.) and limit the simple carbs like bread and fruits.
As for wanting your legs to shape up - how are you training them now? What rep range?
Cardio 6 days a week is a lot. As low as your bodyweight is for your height, all that cardio could be catabolizing your muscle. When the body is overstressed due to insufficient calories and/or overtraining, it will start shedding muscle (to lower metabolism) in preference to losing fat so it can conserve the most energy. Also, a higher proportion of incoming calories may be stored as fat, because the body senses possible famine.
I'd cut out some of those cardio days. On the days you do cardio, don't always go at the same pace. Try doing an interval sprint session (e.g. alternating betw easy and hard pace). This is great for leg and glute definition. 20-30 minutes is plenty and never more than 2x/week as intervals are very taxing.
If you tend to do cardio before weights (and you don't eat something before lifting), either switch cardio to after weights, or eat something after cardio before starting weights. If your body is drained from cardio, you won't get a very effective weight workout.