BMI is Body Mass Index, basically a ratio of height to weight that has nothing much to do with actual bodyfat. It sounds like you're using it interchangeable with "bodyfat percentage", but they're two different things.
What is "FIIT"? I don't think I've ever heard of that training method.
And if you cut 1,500 calories from your diet and train 9 days a week, you'll lose 80 pounds in 4 months. Yay!
Dude, cutting a ton of calories is rarely a good idea. A very general rule of thumb when trying to drop fat is to not reduce calories past 10xBodyweight. So that'd have you at about 1900 calories at the lowest, since you do still need to fuel and recover from hard training.
Start by writing down what, how much, and when you eat. Doesn't have to be weighed out or anything, but it does have to be honest. Simply "Egg McMuffin, hashbrowns, and small milkshake at 9:00am; Snickers bar at 1:00pm; five slices pepperoni pizza at 7:00pm", or whatever it is. That'll give you some type of baseline to improve on.
Both, yes. 3-4 days of lifting and 3-4 cardio workouts per week is a solid place to start. Tons of articles lay out programs that fit that bill.
Your buddy doesn't know what he's talking about. You don't "get into condition for lifting" by not lifting. Find a well-designed lifting routine and start it ASAP. Also, I wouldn't dive right into HIIT if I thought someone was so deconditioned they couldn't handle lifting. Stop asking that dude for advice.