1-is there a way to align the brackets automatically?
2-is there a way of putting more than 1 hairpin per stave? I faked it in this example?
3-is there a way of putting text in the first hairpin like in the other lines? I want to indicate how long the crescendo lasts.
Not really. You could manually position some text there using Shift+X text, switching off ‘Avoid collisions’ in the Properties panel so you can move the text freely, and setting it to erase its background.