You are drowning in information and advice! It can be so overwhelming that you become paralysed. Have any of your neighbours got any outbuildings in their yards or on their land that are a similar size to what you want to build? How are they secured to the ground? Even if you are in an area that gets high winds, the particular place that you want to site the coop might be sheltered? Just decide on a plan and then enjoy the learning process of building it! I have just completed building a log cabin (not for chickens) and it has been a fantastic adventure. I have done anything like it before.