Is what is happening an indication that my repentance for the illicit relationship that preceded my marriage has not been accepted, and what should I do about my husband's threat to expose me to my family?

Allah is Forgiving and Merciful; He accepts the repentance of those who repent. So, whoever repents, believes, and does righteous deeds is guided. What happened with the husband might be a trial, and enduring it raises one's ranks. The husband is commanded by Islamic law to treat his wife well. If he acts wrongly, he should be advised gently and reminded of Allah. Thoughts of suicide are from the whispers of Satan, and it is a loss in this world and the Hereafter. If the husband does not straighten up, the woman may seek divorce, and she should not fear scandal; she can deny it by allusion.