Atouchdown is worth 6 points. additionally you score an extra point if you can kick a field goal . is the total number of points scored proportional to the number of touchdowns

No because a touchdown is worth 6 and the extra points is worth 4 or 2

Sort of because you can also go for two extra points by throwing or running it into the end zone and you may also miss the extra point into the field goal. Also there are safety's where the quarterback is tackled in there end zone which is worth 2 points toward the opposing team and field goals where the ball is kicked on fourth down and they never made it into the end zone which is worth three points for the team if they make it into the field goal.