(Well, Sassy, at least it gives me excuses to infodump about my lore)
This is many questions, I’ll just answer ‘em right in order.
1. For really bad inclement weather, wood sprites wouldn’t go outside, no. They’d bunker down inside their homes and make the best of things … they could find a container around if that was needed.
To keep themselves warm, most of the time they will snuggle together in a group (in Brothers Asunder, young Sam most definitely did grow up knowing of these snuggle piles). Wood sprites also know a few Prayers to help them out in such weather. They can Pray for magic that brings heat through the living tree all around them, and prevent them from freezing in their li’l cuddle piles.
2. Newborns and young babies do use cloth diapers, yes.
Fun fact about baby wood spites (hey, I warned about the infodump): When they are born, their wings are not fully developed. Instead, they have little leaf buds on their backs (which I’m sure their mothers are thankful for, no one wants to birth a set of fully developed wings). These leaf buds stay curled for the first few years of the young sprite’s life, developing into full wings with the help of sunlight. When they are four or five, the buds have reached a thickness of around twice what they were born with, and they start to uncurl. At that point, all flutters break loose as the nestlings learn to deal with the very sensitive nerves that are now exposed to the air.
3. They wash their clothes with water. No, really. Just water. Stones in the stream can be used for scrubbing if needed, but honestly they don’t often need it. Groundwater in Wellwood happens to be extra pure (for reasons), so the stream is extra A-OK to use for cleaning.
4. Correct. Wood sprites are very lax and don’t tend to be super inventive on their own, and usually they don’t need to be. “Necessity is the mother of invention” and all that.