Can I get back to root-able HBoot version by doing a factory reset
No, performing a factory reset won't affect your HBoot version. 

You should, however, be able to follow this guide instead (which uses Revolutionary). There's another page with instructions here which describes in a bit more detail what Revolutionary does and where to go from there. The standard disclaimers with regards to possibly bricking your device apply, of course, and I can't guarantee 100% that it will work.