A bit confused about whether im doing HIIT or not on treadmill, and whether the Interval Training programme is actualy HIIT or not:

My treadmill has interval programme which seems to work to a ratio of 1:2 - ie 1 min high intensity and 2 min low intensity. I'm doing a 20 minute work out on the machines highest setting (level 10), which equates to about 12 mins of interval training with 4 mins warm up and down.

My questions are:

- Does this lend itself to fat loss? Im 213lb @ 27% body fat and goals are to get body fat down to about 15% and maintain lean muscle as much as possible. Im doing strength training, but not trying to bulk up, just maintain lean mass while losing fat.
- Im confused about intensity - does this mean high percentage of max heart rate, or sprinting as fast as you possibly can (perceived intensity)? The latter is difficult on treadmill safely. My max heart rate is estimated at around 185 (220 - 35) and during the intense phase my HR gets up to 170bpm+ (over 90%), HOWEVER, I cant go all out sprinting as fast as i can as the machine doesnt go that fast, at least not with the programme im using
- A question about calorie defecit, exercise and body going into survival mode. If my daily requirements were say 2500 calories and I ate 2200 cals a day, BUT used 500 cals exercising, creating a 800 cal deficit, would my body go into survival mode and slow my metabolism down like it would if i only ate 1700 cals without exercising?