How do I shot gunblade?

1) Seriously though, how to use the styles properly? And which are good for mobbing / bossing?

2) What does Zandi's charged weapon action do? Looks like the animation just ends when you let go of the button

3)How does Purge style work? I thought style is tied to weapon element so it is permanent until you switch to a GS with a different element?

4) Which pas to use for mobbing / bossing? Is voltage gain more important than dps unless there is a major dps difference?

5) Feng Banther's DPS chart lists different values for using a pa's stay / move version after its stay / move version than for using either of the versions alone, Is there something other than Tech Arts Multi Bonus that affects dps for consecutive uses of pas?

6) Enhanced pas come from those 1sp skills for each style?

7) How about this tree (complete rest is here to stay, I'll have >1000% pp regen with 3sp)?
(and I got a bit more deband disorder for fi chase builds)