First and foremost, a big congratulations on losing 30kg of weight!! That's amazing mate. I'm sure that means a lot to you, because I know it takes a LOT to make that initial decision to turn your life around, as you have.
Secondly, there's no such thing as a dumb question as far as I'm concerned. If you don't know the answer, what better way to find out than ask?
In actual fact, it's quite a good question and something that I believe has been quite misinterpreted within the fitness industry. I have certainly heard many people suggest that exercising on an empty stomach is the most effective way to "tap into" the fat stores. The theory behind this is that, because you have starved yourself for in excess of eight hours (whilst sleeping), your body has little carbohydrate to draw upon. Therefore, the primary source of energy is going to be fat tissue right? Unfortunately, the body doesn't work that simplistically.
What this theory fails to consider is muscle mass. Muscle mass is actually broken down far more readily than fat tissue. So, if you are exercising on an empty stomach, you will experience a fair amount of muscle catabolism. Considering that muscle tissue is a classified as metabolically active (in other words, burns plenty of calories throughout the day), losing muscle tissue is extremely counter-productive with respect to fat loss.
That's not to say that exercising on an empty stomach will not result in fat loss. I have no doubt that you will lose fat tissue by exercising first thing in the morning. However, considering that you will sacrifice a fair amount of muscle tissue in the process, there are more effective ways to achieve a substantial amount of fat loss.
Another point to consider is that, what you exercise on an empty stomach, the intensity of the cardio session will be greatly impacted. Think about it - you're running off an empty tank. How hard will your body allow you to push? Not nearly as hard as if you were fully fueled. Therefore, the number of calories during the HIIT session will be greatly reduced. Additionally (and more importantly), the overload on your body will thus be reduced and therefore less fat tissue will be metabolised after your workout has completed.
A good approach is to perform HIIT's about an hour after breakfast so you have plenty of carbohydrates to assist in energy production. If you want to perform low-intensity exercise to burn additional calories, but without the overload on your body, I would suggest to do so after a later meal to prevent muscle breakdown, maybe in the afternoon. Ensure that you continue with an effective resistance training regime, as this will assist in muscle synthesis and also greatly enhance fat loss.
A great article on this topic we have available is entitled "Myths Under the Microscope - Fasted Cardio".
If you need any assistance with your goals, please don't hesitate to contact me. It seems like you have your nutrition down pat with a professional, but do remember that your training is just as important for maximum results.