Okay, I found out that I just forgot to enable alphablending :P But still there is something wrong with the projection causing the offset and the wrong water reflections. The heat refraction should look better now but because of that still not perfect.
I will create an other version of the DoF without fp rendertargets, which will hopefully solve the problems with it.

I will upload a new version if I consider all the current problems to be fixed.
Thanks for testing and I hope that you will try it again later on :P