for 1, I'm not sure exactly what you're experiencing. There are 3 shelves of books in the mage's guild; the top and bottom shelves don't have any content yet. The middle shelf has the new spellbooks. I'll remove the door/curtain because it's a little confusing and the message is kinda incorrect now, but interacting with the middle row books doesn't require you to interact with that door/curtain in any way. You should be able to try to study magic, and if your relevant skill level is too low there's a message saying so.
for 3, I'll dig into this but if anything I'm seeing the opposite, where stamina is regenerating too fast. the "defend" action should regain 5 stamina, and then stamina is regained per turn based on physical fitness (which also affects max stamina). If you ever get into a situation where you'd like to just die already and end the fight, you can press right arrow to skip your turn without taking any action.