Yes :) That is what it means. "Flux" implies rapid change. It is not a verb, however. It is a state of being - a noun. Thus, something "is in flux" if it is changing. "Fluctuate" is a verb closely associated with flux. It means to change rapidly. The economy is in flux. The piston fluctuates as the engine runs.

In a state of constant change. "The state of the euro has been in flux for the past few months." "In flux" is constant, large change - not just a single, or short change.

Yes. That is hasn't settled, it is changing.