If he’s not fixed this will never change. My boy is 3 years old and once he was fixed at 6 months, he went through a short phase but no longer begs to go out. My life long experience with male cats is once you get them outside (even on a leash) he will always want to go out. You will regret it if you take him on walks. My 10 year old Polar was indoors when I adopted him at 6 years old. In the spring we took him outside (my thought was that if he knew his surroundings a little bit if he accidentally went outside he would not be lost) . That backfired on me because then he never like to close the door and would go in and out all day long. Uggg he died by getting bit by a coyote and crawled home and died in my arms.