Install a Antenna craft , HBU33 antenna in the attic.
Aimed at about 2 degree magnetic compass direction.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
Install a Winegard , LNA-100 'Boost' , antenna system amplifier.
For 1 Tv connected use No splitter.
For 2 Tv's connected use a simple common 2 way splitter.
For 3 Tv's connected use a simple common 3 way splitter.
As you are aware , attics Are Not a reception friendly environment and never will be a reception friendly environment.
Reasons:
Multi-path/reflections Tv signals bouncing all around.
Absorbing Tv reception.
Blocking Tv reception.
If reception situations/problems happen that are not resolvable with adjusting antenna aim and antenna location in the attic then move the HBU33 antenna to above the roof in such a manner that reception is not impeded and blocked by the roof and house in the directions of , North West , North , North East , South East.
The HBU33 antenna above the roof is aim the same direction , about 2 degree magnetic compass direction.