Hi Ali,
Your throttle setup looks good, as long as your getting a linear throttle movement and your servo output arm length match the engine carb throttle control arm you should be good to go.
What i usually do to make things easier when setting up is first get the throttle linkage rod and set the ball links on each end so that when put up against the servo and throttle arm on the carb i can see the servo output spline screw through one ball link hole and the bolt in the throttle control arm through the other ball link. I generally do this with a vernier gauge but this is can also be done by eye.
Next, set the ball on the servo output arm and throttle control arm on the carb so that the distance is exactly the same or as close as you can get depending on what servo and arms your using. I usually find with OS carbs that 17mm is the sweet spot if memory servs me right!
Next, power up the radio system and set 50% throttle and then loosen the bolt securing the throttle control arm on the carb. Next i fit the throttle linkage rod and you will notice there will be a hole in the carb extension arm, what i do is use a Hex/Allen key tool in the hole and position the carb so it is at the 50% throttle mark then tighten up the bolt securing the control arm to the carb.
I have used this method for years and it usually give me a very good mechanical setup with very minimal travel adjustment required.
Hope this helps, and any questions just give me a shout.
Cheers,
Ross