Is there anything that indicates the superiority of standing directly behind the Imam in the first row, and what is the ruling on one who reserves his place behind the Imam by placing a personal item?

There is no authentic hadith proving that praying directly behind the Imam is better than any other place in the row, and the narrations to that effect are weak. Authentic hadiths have been narrated indicating the superiority of the right side (maymanah) of the row, among them the saying of the Prophet, peace and blessings be upon him: "Indeed, Allah and His angels send blessings upon the right sides of the rows," and that the Companions loved to be on his right side, peace and blessings be upon him.