You need to ascertain your active BMR (the calorific figure need to maintain your current weight based upon your activity level). In order to ascertain this figure, if you’ve not already done so, research BMR calculators as they’re largely accurate in determining daily calorific needs.
However, BMRs vary between individuals, since they also take into account a person’s age, height and weight so it’d be impossible to state what yours may be.
Since you don’t really have a lot of excess visceral fat covering your abdominal area, I’ll re-iterate that you shouldn’t consider introducing a daily deficit that is too severe (a maximum of 250-300Kcal per day), as HIIT expends a lot of energy (calories) both during and after its endeavour.
It’s equally important that you re-fuel with carbohydrate following HIIT sessions, as the effort creates a huge increase in your insulin sensitivity. Such an increase means that the carbohydrate, that is broken down and converted into glucose, is far less likely to be stored as adipose tissue and stored in the muscle cells as glycogen instead (remember the huge energy deficit created).
Don’t make the mistake of thinking that you can recover from HIIT through consuming whey protein alone. Granted, un-flavoured whey contains all of the amino acids needed for growth and repair of damaged muscle fibres, but it doesn’t contain sugars needed for replenishment of depleted glycogen reserves. Immediately following HIIT, simple sugars are the quickest way to begin replenishing depleted glycogen reserves.
In the hours afterwards, although your insulin sensitivity levels will still be significantly raised, your carbohydrate intake should be obtained from complex carbs.
As for a breakdown of macronutrients, in order to ascertain how many daily calories should be obtained between protein, carbs and fat, research macronutrient calculators. Also keep in mind that if you’re exercising intensely, you should be consuming around 1g of protein per lb of bodyweight.
Lastly, if you’re concerned about the catabolic effect (the breaking down of protein to be used as fuel), there’s very little need to worry. The intense periods and the overall length of the session simply aren’t long enough to be of detriment. If anything, you’ll possibly find that HIIT cardio sessions also begin to increase the size of the muscles in your legs due to the increase in ATP density of the muscles themselves.
The added benefit of increased ATP density leads to increased power and reduced levels of fatigue in the muscles, during both aerobic and anaerobic exercise.