Couple of suggestions. Seal the hinge line on the elavator with some clear packing tape. And replace the push rods if you feel they are to weak.
Try a higher torgue servo if you can get one. Yours looks like a standard one that comes with the radio.
Also go with a 12x4 or 13x4 prop. The 11x5 can still generate to much speed even at lower throttle settings.

Good luck and have fun !!!