Okay so I tried the config_hd4600_4400_4200.plist and it worked and made install USB boot correctly. So I tried with the already existing El Capitan installation and it worked and booted to desktop. Amazing. But now Audio and Wifi aren't working, wifi says hardware not found BUT Bluetooth works. I tried putting back broadcom wifi kext and changing to Macbook 6,2 in config.plist. Also tried patching and adding DSDT, SSDT-1, SSDT-2 and SSDT. Still the same problem.
Sleep works though. After sleep wake up, trackpad and Bluetooth stop working. Tried rebuilding kextcache as well. Attaching ioreg and other outputs below.