The basic hardware looks to be up to the task...
Get rid of the dual clevises.
You only need adjustment at one end.
The connection to the surface. What is that? How securely is it installed?
I've had something like that flutter the wing so badly the slip-on nose cone on the glider came off in flight!
You mention it's a moldie.. the whole servo as mentioned could be moving with the skin.
Pack some stuff around the servo.