The linebacker with the most sacks in an NFL season is Justin Houston of the Kansas City Chiefs. He finished with 22.0 sacks in 2014.
In 1981 Klecko had 20.5 sacks and Gastineau had
Elvis Dumervil of the Denver Broncos. He had 17 sacks.
Michael Strahan had 22.5 sacks in 2001 for the NY Giants.
The 1984 Chicago Bears who had 72 sacks.
The Chicago Bears hold the NFL team record with 72 sacks in 1984.
There isn't really a record kept for fewest sacks in a season by a player, as there are thousands of NFL players who have not had any sacks. Michael Strahan holds the record for most sacks in a season, at 22 1/2.
New york giants
Mike Berg of the Green Bay Packers had 9 sacks in the 1979-1980 season.
Unfortunately, Karras retired after the 1970 season. The NFL did not begin recording sacks officially until 1982.