Someone might think this because if they are new to fanfiction or only really follow a particular subset of fanfiction related to Izuku Midoriya. For instance, if they mainly read stories from a specific website or group of writers who focus a great deal on Izuku Midoriya, they may not be exposed to the wider range of male heroes in fanfiction. Also, if a person is really attached to Izuku Midoriya's character arc and story, they might subconsciously assume he is the only male hero in fanfiction without realizing the vastness of the fanfiction world.
Yes, there are. However, their availability might vary depending on your location and the specific comic publishers. Sometimes, limited editions or special releases of All Might comics can be harder to come by.
Definitely not. Midoriya's character is very much alive in the manga. The creators have no intention of killing him off as he's a key figure in driving the narrative forward and inspiring other characters.
His closest friends like Ochaco Uraraka and Tenya Iida would most likely side with him. They have always been there for Midoriya and share his values of justice and doing what's right. Also, those heroes who have seen Midoriya's growth and believe in his pure intentions would probably join his side.