Had a friend that after drying and curing he would put all his bud in jars and into a cooler. We dug a hole put the cooler in the hole and kept his bud in the ground for months taking a jar when he needed and filling the cooler when he cropped out again. It's in New England, many times we had...
Imo I flush at the end. You have a short flower time (8-10 wks). I only flush during flower if there is a reason to. Other then that pump them full of nutes. It's your garden but you may want to rethink all that flushing and wait until the end.
Don't know how big your room is but my sealed room is 20x12 I run 2 dehumidifers to keep it all good at 45%. Without my dehumidifers my rh goes to the 70's+
I was told not to seal my room without c02. I've never run without it sorry can't help with this one.