2. No it didn't install without errors when you ran the RUU, that would never have worked, ever. You just didn't see the error because you used the RUU executable. Check the logs in c:\ruu_log and you'll see it never installed hboot.
3. The instructions in post 3 of this thread are quite clear on how to downgrade. If you used the other thread then you didn't read the first line of post #1 in that tread.
4. No you won't be S-OFF after a downgrade, rerun revolutionary.