Sounds like you're vastly oversized, which will cause wide temperature swings and short cycles. Not comfortable.

If as I suspect, you want to slow down the blower, it may not change the situation drastically, and you could run into other problems.

V

Does your furnace have a cycles per hour setting? If it does it is probably set to 6. Try a setting of 3. This should lengthen the cycle times.

You will need to find the manual for the furnace to figure out how to change the fan speed. I think A is the fastest, but I am not sure. A slower fan speed will translate to a higher furnace temperature. If the furnace runs too hot it will trip the limit switch and shut down. Running hot can also lead to other problems like a cracked heat exchanger. I suggest you don't change the setting by more than one speed.