About the initial question, cf. Awake! 2/8/2003 p. 12-13:
Why do true Christians take the warning of the unforgivable sin to heart? Because although we have accurate knowledge of God and of the activity of his spirit, a wicked heart could develop. (Hebrews 3:12) We should be careful not to think that this could never happen to us. Consider Judas Iscariot. He was once a faithful follower of Jesus. He was chosen as one of the 12 apostles, so he must have had good qualities. But at some point he began to let wicked thoughts and desires grow, and they eventually overtook him. During the period of time he was an eyewitness of Jesus’ incredible miracles, he was stealing money. Then, for money, he knowingly betrayed the Son of God.
Some people who were once faithful Christians have purposely drawn away from God, perhaps because of bitterness, pride, or greed, and are now apostate fighters against God’s spirit. They willfully oppose what the spirit is clearly accomplishing. Have these individuals committed the unforgivable sin? Jehovah is the final Judge.—Romans 14:12.