Ouch - looks nice - but flamethrowers -
are very, very dangerous.
The fuel is basically unstable. You have to keep it pressurized, which in itself, can cause problems.
You also have to worry about flashback, that is where the flame goes back up the pipe into your fuel source. (badda boom)
On most movie sets, they have three guys standing there with fire extingushers, just in case (foam even), and they use propane gase in very long pipes going to the "smaller" self-contained flamethrower (allows time to shut the thing off incase of flashback).
As others have pointed out, your costume is made up of highly flamable items.
I would not recommend for you to attempt this unless you very aware of the dangers and have working knowledge of gases/flame/materials.