I did not get you.
your animation has a limited and fixed duration and it is not possible to hold spacebar to stay in the air for a longer time.
after you press spacebar you must first set movement mode to fly and then play jump animation and then you have to determine when animation is gonna finish playing to set movement mode to walking at that time.
i think the best way is using an animation notify
no need to do any thing when releasing spacebar.
use an animation notify to set movement mode to walking again.
