Ok, we've got lots of things going on here.

First, the Yaw thing is not unusual at all. Here's what usually happens:

You're traveling down the runway adding right rudder to counteract the torque and steer it straight. As you lift off, most people instantly release the right rudder input - not good. Maintain that rudder input and slowly release it as you climb out.

Next, Are you flying from grass? If so, the grass may be impeding your takeoff speed which will keep a less-than-ideally powered plane from reaching it's takeoff speed very quickly. Note that this will also lead to taking off with a little less speed than what would be ideal, which will also add to the yaw problem.

Finally, if you want more elevator control, you can indeed move the clevis closer to the elevator, but do not move it closer to the servo - that will defeat the purpose. The pushrod does NOT need to be at 90 degrees as you stated.

The further OUT you go on the Control Horn, the LESS control you get.

But the servo end is just the opposite

The further OUT you go on the Servo Arm, the MORE control you get.