1 - He was keeping and following the laws of the pharisees which were full of leaven.
Paul was among the best of the Pharisees.
Following the law on our own is self-righteous. We should have righteous that comes from God.
Full of leaven! The Pharisees! How about full of love and compassion for their fellow man Jesus? If you need an evidence or two, they, the Pharisees tried twice to save Jesus from being arrested and taken to the cross. The first time was from Herod who had sent his men to arrest Jesus and the Pharisees, undercover, went to Jesus and revealed him the secret. Jesus listened to them and saved himself from being arrested and death. That's in Luke 13:31.
The second time was from Pilate when Jesus' disciples were acclaiming him king of the Jews in Jerusalem and the Pharisees went to him and warned him to stop his disciples or he would be arrested. Jesus waved out their warning perhaps because he was enjoying the parade and said that if they stopped, the stones would shout. (Luke 18:37-40) As a result, not too long afterwards, Jesus was arrested and condemned to the cross on the charge of INRI. The point here is only to show to you that the Pharisees were not so full of leaven as you claim they were.