All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
A person who persists in listening to music after knowing that it is forbidden is considered a dissolute person and he should not lead the Muslims in prayer. The scholars differed in opinion with regard to the ruling of praying behind a dissolute person. In Fatwa 88729, we stated their views and clarified the most preponderant opinion, so please refer to it for more benefits. You may also refer to Fataawa 81239 and 81545 about the ruling on music.
As regards your statement whether or not you will be forgiven for all the words that you said, you have to know that if a person sincerely repents from his sin, then Allaah will accept his repentance and forgive his sins, and He will not hold him accountable for them on the Day of Judgement. This is indeed a Mercy and Favour of Allaah on His Slaves. Allaah Says (what means): {Say, "O My servants who have transgressed against themselves [by sinning] do not despair of the mercy of Allaah. Indeed, Allaah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful."}[Quran 39:53]. Allaah further Says (what means): {And it is He who accepts repentance from His servants and pardons misdeeds and He knows what you do.}[Quran 42:25]. In the same vein, the Prophet said: "Allaah accepts the repentance of a person as long as he is not breathing his last (i.e. dying)." [Ahmad and At-Tirmithi] So, if you repented from the words that you said in which you sinned, then we hope that Allaah will accept your repentance; for the conditions of repentance please refer to Fatwa 87903.
As regards the speech that is not beneficial, if it is permissible, then a person will not be held accountable for it Inshaa' Allaah. Indeed a group of our scholars from the Salaf said that the angel only writes the acts which a person is rewarded for or sinful about. This is the view of Ibn 'Abbaas and 'Ikrimah .
Allaah Knows best.