First of all. Uninstall your bootloader from your OSX disk. You must boot the windows 64 bit installer in UEFI mode (UEFI bios) and install to a GPT formatted disk. Do this first, and install a program called EasyUEFI once windows is working. In BIOS settings disable windows 8 features. Next boot from a clover USB to your macOS disk. Run the clover installation package with installation target as the same disk you installed windows UEFI to. Install UEFI only in ESP. Use EasyUEFI in windows to change the boot order and make Clover the default loader if Windows is starting every boot. So in answer to question 1) windows 7 requires a fresh install, and 2) your macOS drive will boot from clover either way.