If you need the cable to be stiff in a certain area , wicking a little solder in the weak place stiffens the cable . and the cable pushes just fine, if you have it set up right. Dont cut the tube at the bulkhead , where it comes into the radio compartment . Cut it a 1/4 inch short of the sevo arms farthest forward throw. If it still flexes alittle , add a standoff, to support it. Heck , most the time I use a micro servo , they move that freely .
Most throttle arms have a set screw so you can rotate the arm. Most , if not all my installs have been with the arm up. . Just seemed to work out that way.
If your wire flexes to easliy, you may be using to soft of metal rod or if you have done a lot of bending on it , have taken the temper out of it. All the fixes mentioned should work for you, not sure what you`ve got going on, but dont give up.