Download and launch Chameleon Wizard, latest version is 4.4.1. Click on org.chameleon.boot.plist tab. There on the right, you'll see the option to check kext-dev-mode=1
Current myHack/myfix I believe is not Yosemite ready. Delete /System/Library/Extensions/myHack.kext
Install the updated kext linked above to S/L/E with kextwizard.
It's probably not initialized properly. Try repairing cache and permission.
The FB patching actually revert it to 10.9.2. The one from your link seems to use FB from a Desktop or faking it.
I can confirm patching libCLVMIGILPlugin does help with the preview. So use it if you also have the same problem.
The MBR patch from myHack has some dependency issue. If you really need to build on an MBR partition, then you'll need to replace the MBR patch file.
Use the version of patch for the version you're installing from here. No need to rebuild the installer.
Otherwise, just use GUID and select no when you build the USB Installer.
Start with Herve's guide. Very close to your model. Only thing I could think of is you might have a broadcom ethernet card. We could determine that later or you could list your system specs.
CPU:
GPU:
Display resolution:
etc...