how long should I veg my king tut with out outgrowing my tent. running two 600 watt led each plant has there own light.

That's way for you for work out. You need the manufacturers guidlines for hanging in flower, and that will be your maximum plant height. You can use some LST which I think you are there to keep her growing low and flat. She will at least double bite slow for nearly tripple in height. I would do another couple of weeks of training and then flip.

all of them together :) not individually or the math won't work out

when the L x W dimensions are 2/3 to 3/4 of ending size you want.. should be safe. So a 3x3 should be roughly 2x2 or a bit bigger, but not much. (.66x.66= 43% or room for ~2.5x growth room and .75x.75 closer to 2x growth room) Some strains stretch more than others after switching to bloom. What i suggested covers 2-3x growth.