Hello Carlos! Thank you for the kind words and thoughtful feedback! Allow me to answer your questions in order to hopefully shed some light on certain aspects of the game.
1. Currently the High Elves and Wood Elves have the same songs as the Humans of the Wilds and the Empire. I thought about writing them all different songs, or perhaps a selection of mixed songs, but after testing I was not satisfied with the balance across 36 options, and therefore limited them. However, to your 2. point, I am currently working on a supplement for Wilderlands with some additional rules and guidance (think Deep Cuts for Blades in the Dark) which has both rules for Wizards if you wanted to include them, the thought process behind creating Songs and Items of Power for those GMs wanting to expand the list, and some other odds and ends advice.
3. The text on page 15 could be clearer, but the D6 roll for your Calling is in fact also your stamina! For example, rolling a 3 for Treasure Hunter means you get 3 stamina and the additional starting items for your character. The Callings are balanced around the higher Stamina entries providing less useful starting inventory.
I appreciate any and all feedback, and would love to hear how your experiences running or playing Wilderlands go for you! Hopefully these comments are helpful