I have an odd question to ask, but it's very important. If I ever wanna get published, I need to be versed on copyright. You see, my inspiration for writing is always a story that angered me. Something happened I REALLY didn't like, and I was angered enough to actually write a redaction. So I sorta am a fanfiction writer; except that for the most part I try and make it my own. For instance, I REALLY hated the ending to Lovecraft's 'Shadow Over Innsmouth.' For that matter, I have everything about Lovecraft as a writer and a human being. So I'm yanking Innsmouth out of Lovecraft Country, putting it in MY universe, and writing a story where Innsmouth has been rebuilt, and a descendant of Orbed Marsh, Dr. Logan Marsh, runs the Innsmouth Clinic, which is essentially a hospice for people with the Innsmouth Look. Using the text of 'Shadow Over Innsmouth' and simple logic, I make the alternate interpretation that the Deep Ones are vastly delusional about the scope of their power, wealth and ability to dominate humanity. In another story, "Lost Generation" British WWI vets use then modern war equipment to free their village of Hampstead from the Cultists, and then utterly slaughter the Deep One counterattack. Cosmic Horrors from beyond the Cosmos are a part of the tension, but both angels and demons fight them relentlessly wherever they try and breech into that universe. So I'm taking ideas, and contorting them to do what I want, in my own universe. I'm making them my own. And I know there's such a thing as fair use, and that there comes a point when something is sufficiently different copyright no longer applies (like Nosferatu from Dracula), but I have no idea what these exact rules are, nor where to find them nor how to use them to make my stories publishable. So I'm asking for help, because it would make writing a tad easier without copyright violations breathing down my neck. Any help is appreciated.