Sucks about the dead seedling, I have had some bending over issues with seeds before, I tend to stake them with toothpicks until they can stand well on there own. I also will not necessarily have any fan blowing on them at all, from what I understand just having a vibration in the room will cause the stalks to thicken as well, as long as the pots are getting some of that vibration.
With your open area I would not be too concerned with in ventilation, you need fresh air, but your area is big, and will take a while before you need to be extracting air.
I would not worry to much about your plants, some will live, some will die, but you can always make more. Growing weed does not require much work, and you have like 4 to 5 months to do the work in. Take your time and enjoy the experience, I find it very soothing working with my plants.
With your open area I would not be too concerned with in ventilation, you need fresh air, but your area is big, and will take a while before you need to be extracting air.
I would not worry to much about your plants, some will live, some will die, but you can always make more. Growing weed does not require much work, and you have like 4 to 5 months to do the work in. Take your time and enjoy the experience, I find it very soothing working with my plants.