Signal attenuation and signal reflections bouncing around (multipath) make attics a Non friendly reception environment.
The Tv transmissions at your location are Very Strong Signal Strength.
Install a ANT751 in the attic aimed at about 110 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing.html.
No amplifier will be required.
If there are reception problems that are not resolvable buy moving or aiming the antenna in the attic , then move the antenna to above the roof.