how to increase mpg

10 mpg is reasonable if you live in the mountains. I got 22 mpg average hwy in my 69 Dart slant for decades, in flat land. The best way to get mileage is to never use the brakes. Everytime you brake, you waste energy. Ride a bicycle and you will appreciate. The 70's "gas crisis" recommendations to "accelerate like an egg is under the pedal" is only partly true. A gas engine is actually more efficient at WOT, but when the carb starts enriching the mixture (max power), efficiency drops. Thus, OK (even optimal) to accelerate briskly as long as you don't floor it and go rich. Also, don't accelerate hard just to brake at the next red light or traffic jam (obviously stupid).

If really motivated, install a wide-band O2 sensor in the exhaust, or even a simpler rich/lean indicator. Without that, you are "flying blind", unless you regularly remove the spark plugs to try to discern rich/lean and that isn't even in the same ballpark. Hardest part is welding a bung in the exhaust, though that isn't hard when reworking the exhaust. I always install 2 bungs so I can use an on/off O2 sensor to verify the wideband sensor.