The MacBook you have has a 1.1Ghz mobile CPU, so I doubt you will ever get good speeds in the GameGuru editor, that is far below the min specs for GameGuru and that is even before running in a VM that is sharing those resources. You also have quite a weak GPU that is below min specs, but that isn't as much an issue as the CPU.
The MacBook you have is not intended for graphical intensive programs. However I have a Macbook Pro Late 2013 model and that runs GameGuru perfectly in a virtual machine.
Windows 7 Pro, Intel i7 3.8 GHz (Passmark: 9021), 16GB DDR3, NVIDIA GTX 780 4GB Superclocked (Passmark: 8056)