Baked texture doens't fit onto UV map.

Hi. Ok so I’m doing some work for a project using the Ogre3d engine and have to build some models. Some of these are rocks and one in particular is a rock arch. Because manually creating a texture would be annoying I settled for a procedural texture that I wanted to bake onto the UV.

Problem: It won’t bake it fittingly as you can see here:

Does one of you know where it went wrong?

Another problem you might see is the texture stretching on those sloped faces that I can’t get rid of.
If you have an idea how to solve that I#d be very grateful.