I don't know if these are true but they seem likely
I am quite sure that playfulness affects spirit pleasing. I have had high / very high playfulness explorers with maxed spirituality displease spirits multiple times, but I don't ever recall a low playful explorer with max spirituality displeasing. In general, my explorers that often displease spirits have high playfulness. Also, WP uses flavor text to give hints to what stats do what in explore, and when a spirit is displeased it says something like "your wolf wags tail playfully"
Sometimes I feel as if desert has a higher chance of finding items to dig. But maybe I'm just trying to find redeeming qualities in the desert.
I believe weight variance of pups is +10/-10 the average of the parents' weight. Within this range, weight distribution is random than a bell curve.
And how inheritable are dynamic pelts? I've heard others say that it's not at all inheritable (like other non-common traits) but I'm pretty sure ptarmigan feathers are much more effective if the parents have dynamic coats.
Well dynamic coats cannot be inherited as they are randomized. The chances of getting a dynamic pup with a dynamic mother/father is low. However yes the ptarmigan feather does higher the chances for randomization. So no dynamic coats aren't really inherited, they're randomized. I don't what the percent, but it's pretty low I think.