Yes this won't work because like it says it needs version 3.50 or later, now it might be exploitable but the update.pup file has version 3.41 but also need to tell the PS3 it is version 3.50 or later. The PS3 isn't stupid though it knows what to do...
Downgrading will NEVER work. And I doubt jailbreak will ever work with any firmware other then 3.41 and lower. If you want to jailbreak go buy a 3.41 off craigslist.