Enjoy the fruits of your efforts! Way to stick with it!
Thank you, Paul. Thank you to everyone who has helped me. I followed most of your advices and others I'd like to share with you. A couple of days before the brewday I was talking with a friend of a friend, who works in a biothecnology company. I explained him my problem and told him I had bought an ozonizer. He suggested me that I could saturate water with ozone and them use this water to clean all the stuff and all the surfaces of the brewplace, including floor, walls, ceilling and, above all, doors and windows, taking care of those metallic parts, as brew kettles and valves (he told me I should soak them for 10 minutes at maximun, cause ozone can damage stainless steel), but I wouldn't care about plastic or glass items. So I did what he told me, then I rinsed with water and finally I soaked with Star San and drained. Furthermore, I ozonized the brewplace during several hours.
I don't know if ozone has been the core of the lack of infection (I keep my fingers crossed), but I've thought some of you can find it interesting.