....
I'm not sure if I'm following your grind on the tool. Part of the problem
is that your bar is sticking out over 4x its length, so deflection will be
an issue. Once you have anything over 3-4x the diameter hanging out of the
chuck, you need to think about supporting the work, usually with the tail
stock. The other thing you need to do is keep the cutting forces low. This
....

You gotta fix this to have a chance. Chuck in closer for this cut? Time to
build/buy a follow rest?

Karl