FA-Q.

1 hit, though you have 6 chances to activate it I think.

Only skills that have a variable number of hits/MP cost (e.g. Hurricane) can activate FA on every hit.

No. 1 hit, 1 chance to activate FA. 1 u.strafe has a 40% chance of activating FA.

FA is no-delay, it just pops on there as a little extra damage. In the past, it was it's own attack and interrupted other attacking skills so it could hit, but now it doesn't interrupt anything, you just attack normally and it'll do it's own damage independently (with a little red pop where your arrows hit).