Why are you eating low carb?
Generally speaking, like Stu was getting at, low carb diets and high-performance athletics do not go hand-in-hand. There's a saying about "earning your daily carbs" through hard training. From what you've said so far, you're definitely "earning" plenty on your training days.
What, exactly, did you eat yesterday?
Yes, details please.
What did your last workout look like - exercises, sets, and reps?
High rep, light weight circuit training is a terrible plan for a fighter.
Metabolic Drive is great stuff, but you might want to consider making whole foods your number one protein source.
No problem with these.
That depends on your particular goals.
I'm presuming you're a fighter, but what's your fight schedule like? Do you have fights/competitions on a regular basis?
Leucine is actually one of the branched chain amino acids, so it can be important, but I have a feeling you're getting muddled down with details before you have the broader strokes in place. You're looking to use supplements to achieve what could be done with a better nutrition and training plan.
You're training six hours a day, how many days per week?
I'm really interested to see what your weekly plan is. What days are the "weights" (more like cardio the way you're doing it), what days are classes, sparring, etc.
Also, what's your current height, weight, and general bodyfat level (not percentage, but are you already ripped, lean/average, kinda pudgy)?