yes, i would plant them out in the dryest part of the yard
you might have to water them a bit during dry spells until it grows deep roots.
they are VERY water tolerant when they are larger
and yes, they like all the sun you can give them.
Moringa grows a deep tap-root
and when in a pot, you should make sure that you have a deep container also.
dont let the tap root wrap around it.
i know someone who cuts the tap root when going from small to larger pots,
but you would have to research that first.
also, not every yellow leaf means too much water.
they can loose leaves when they grow normally,
and sometimes they get yellow first.
i know i cant water mine everyday, or they will get yellow leaves,
but mine are between 2 and 4ft tall
i had one that got about 10ft, it died in the freeze last year
when it got down to 25F for a couple of days.
had it mulched well too.
also, you may want to keep it pruned
when it get 3-4 ft tall, cut off the growing tip(s) to bush it out.
they have a habit of growing like a pole if you dont.