You can further adjust this using the endpoint settings on your transmitter. However, I think it's better to get the mechanical side setup as accurately as possible first.

The amount of throw/steering you have in either direction can be best measured by using a setup station. You could do a simple road test by driving in small circles at slow speed both left and right checking that each direction has the same turning circle, however this method can have other variables impacting the results, such as the diff providing different power to each wheel, different toe settings from left to right or bent components from left to right and front to rear. So really the best method is to use a setup station.