My Windstar 2002 LX van I bought 3 months ago.

My windstar 2002 LX van I bought 3 months ago with over 200000 millage has the following issues:
1. Consumes a whole lot of gasoline fuel. 10 liters or more of gas is consumed in less than 50km. With 100 liters of gas, I barely cover 400km and this makes a big hole in my pocket and very frustrating too. I didnt discover this when I bought the car until I traveled to my base with it and no guarantee from the seller covers this.
2. When engines is started the first time in the morning or after long hours parked, idling is normal but when I drive, in less than 10km or when engine temperature increases, engines stalls anytime I step on the breaks to bring the car to a halt or when for instance climbing a bump or in a traffic. I will have to start the car again, keep my leg on the gas pedal and engage to drive before I can move the car, this fault only started recently and I understand this is not health for my car if I continue to forcefully engage the gear.
3. My break light on the dash board is permanently on and the hand break doesnt work even after changing the rear break pad which my mechanic said was bad. The break light still remained permanently on.

my mechanic said my MAF sensor is bad and thats why 1 & 2 above occurs. Although my check engine light doesn't come on at all which keeps me in a more confused state. The MAF sensor is expensive here and I need professional advice before carting away with my hard earned money. Pls advice as I will appreciate your input.