You're trying to make too many things square. Only two things need to be square. Both square up with the pushrod.

The pushrod should make a right angle with the servo arm. The servo arm does not have to be square to the servo case. In fact, the servo case means nothing at all to the rigging of your model. When you're setting up your rigging, at the very start, turn on your TX and RX and center all trims. Then make sure all centering is at zero. Everything works from there. To set up every servo arm on every surface the next step for each is to hold that pushrod where you figure it'll wind up when the surface is at neutral. THEN put the servo arm on the servo gear so the arm will make a right angle to the pushrod. Your first picture shows the servo arm pointing straight down. It won't make a right angle with the pushrod pointing down like that. The pushrod is going to point up at the elevator horn, not straight back. And the right angle required if between the rod and the arm, not the arm and the servo.

OK so far?

NOW comes the tough part to explain. So I'm going to go look for some pictures. The style elevator horn you have is going to cause a lot of explaining.

OH BTW...... lots of designs position the elevator servo lower and run the arm up instead of down. They do it that way on purpose. You've just discovered that purpose.

edit I decided to use your picture instead.