Remove the Freehub

[LiamW]

Longer bit of tubing to fit over the allen key to provide more leverage. Failing that, hit it with a hammer.

 

[Yellow Saddle]

i'll take a look

Just to save another to and fro, if it is at least 10mm, then it should be strong enough to survive a rattle gun attack. See if you can find the equivalent mm 1/2 inch long-series hex socket and take it to a tyre place. They will have a rattle gun and will remove that chop-chop. However, they seldom have hex sockets because they don't use them for removing wheels. Maybe you are lucky and find one with the right socket.
It is amazing how fuss-free removal with a rattle gun really is. I've always had one on standby for our workshop where some BBs and plenty of screw-on sprockets often gave us trouble. The problem with putting these things in a vice is that the home vice is seldom up to the task. Sometimes the vice flexes and rounds the tool. Other times the "team" rips the vice right out the workbench.
Not sure if I've mentioned it, but it is a crap design.