Is my remorse, prayer, desire for repentance, and my Salah accepted, despite the presence of someone who is threatening me and delaying my repentance from a grave sin that I did not commit intentionally?

You are obligated to hasten to repentance immediately. It is not permissible to delay it because of this person's threat. The conditions for repentance are regret and a firm resolve not to return to the sin. If he has a right, you must seek his forgiveness. There is no harm in supplicating to Allah to keep his evil away from you. What is suitable for this situation is the supplication that the Prophet, peace and blessings of Allah be upon him, used to say: "O Allah, we place You in their throats and we seek refuge in You from their evils."