Typically Caps don't like to fly heavy and adding a .61 would definately add a few extra ounces that will most likely make the plane even more squirrely.

If you want to add more power and try hovering go to a four stroke. A Saito .72 is roughly the same weight as the .46 you already have in the plane but is a clear winner in the thrust department swinging a 13 - 14" prop rather than an 11" like the .46 does. Other than relocating the throttle cable and trimming the cowl it's almost a bolt in replacement for the .46.

Also, adding a .61 will require adding weight to the tail to get it to balance if you can't shift enough gear around to get it to balance properly, bringing up the overall weight in the process which is a no-no with Caps like I said earlier.

As for the control rods, ditch them. Excessive flex in a control set up is an absolute no go with a 3D plane. Do the best you can to get ALL of the slop and flex out of your controls and you'll be amazed at how much better the plane flies. My personal favorite on .40 sized planes are the Sullivanwith 2-56 wire pushrods that run through the red tubes. When installed correctly they can result in a very stiff and exxective control system that doesn't shrink or grow with temp changes like the golden rods do.

The twisting out with full elevator input is the result of over controlling the pitch of the plane. This is pretty typical of aerobatic designs like the Cap. Moving the CG back, making sure the lateral balance is dead on and getting the correct amount of right thrust dailed in will help lessen the tendency for the plane to "snap out" like your describing. For normal flying Caps only require a small amount of elevator throw, less than 25 degrees is plently. For 3D the requirements are for much more but then you have to do all of the things I just described in order to lessen the natural tendencies of the plane to snap and make if more controllable.