Is working for a non muslim government permissible in that which is halal like in IT for example? And what about working in a factory that produces vehicle parts and sells them to a non muslim military?

Yes, working for a non Muslim government in work that is itself lawful is allowed, and the Permanent Committee said there is no harm in a Muslim hiring himself out to a disbeliever when the work he does is permissible. As for the factory, Allah knows best.