I responded to your other post, I didn't see your new one.
You don't need an EFI partition. Looking at your setup, I would install the boot-loader on the OS X partition, as you have already using iDeneb (so you don't need to touch Windows)
What I would do is use Windows to remove your OS X partition (after backing it up), then -still using Windows- make two partitions in place of the OS X partition, one for your main OS X install and the other one for a temporary iDeneb install that you can use to work with OS X. Make the second one about 10GB, and the first one as big as you can. Then you should install iDeneb on the second 10GB one. Once you have that, download this bootloader and install it selecting your OS X partition (the first "big" one). Once that is done, post your current iDeneb kexts here and any things that aren't working, and I'll try to figure out what you need to have SL working, but no promises on that.