Depends on where the humidity is at...65% I burp once a day and leave it open for an hour and if it is higher than that burp it twice a day. Check it a couple of times a day. Once it hits 60% I just leave it sealed.
I cut mine off the stems so they fit better....leave enough room in the jar for some air movement. As for the grassy smell...it will go away the longer you cure. I keep one of these in my cure jar until I know it is safe to keep it sealed up...
You might just want to get a couple of cfl's since that baby is so much smaller, that way she won't continue to stretch. You can probably lower that 400w to about 16 inches above the tallest plant and be good.
Put your hand over the tallest plant...if it is to hot for your hand it is to hot for the plant. Try getting a couple of cfls to keep close to that baby!!
I hope you didn't plant more than a couple...that rez is way to small to support very many plants. Add some more cfl's around the sides or your plants will stretch in order to reach the light.