Is there a way to write code that will extend the servo rotation to 180 degrees. Rotation seems limited to around 100 degrees.

The VEX 3-wire servo has internal mechanical stops that limit it's motion to 100 degrees. This is not something you can change in software, but there are other servos you can hook up, and ways of physically modifying the servo to change the range of motion, or remove the mechanical stops altogether.

Before you do so, though, if you're part of a competition, you should see what their official rules are regarding using other servos, or modifying your own.