Ill say this again in here, there is nothing you can flash that will get you back to s-on.
You will need to fastboot command:
fastboot oem writesecureflag 3
so feel free to flash anything in the development section knowing that you wont loose s-off status.
as for going back to stock. flash the ruu in dev section and you'll be back to 99.9% stock (-minus s-on flag and bootloader locked)