I think 12 weeks is closer to minimum than maximum

I'm pretty sure he's fucking with you. He's trying to give you advice, try to look into it instead of pushing it away immediately

15 lbs of fat in 8 weeks is a lot, that's being in a deficit of 937.5 calories/day

15lbs, and 15lbs of fat are two different things. He is going to probably drop 5-7lbs of water/glycogen with it.

But just think about how the body functions, and how it does not know what you are doing when you diet, so it just thinks to survive. Your body wants to hold on to fat stores, and after prolonged periods of dieting, your body is going to feed off of other energy stores.

Carbs are supposed to be low when you cut.

your mom tell you that?

That sounds pretty normal. Try it and monitor that for 2-3 weeks to see if anything changes.

You don't lose anything, drop them down a little more.