#1 He lied about having a meeting with Gravano one time and even worse Gravano was being used by the feds as a star witness against Gotti, so the feds didn't want him undermining Gravano because of his star witness status.

He tried to inform the feds about two corrupt NYPD detectives without realizing the feds didn't want that out in the open.

#2 About 18 months.

#3 Because he is retarded.

#4 Shelve him? I think Vic wanted to kill him.