Was I wrong to leave the marriage? My ex-husband tried to kill my son and me. He told me that he was a baptized Christian. Then he said he was Catholic. After that, he said he did not believe in God at all and cursed His name many times. I have since remarried, but I wonder if this was done in sin?
It isn't wrong to leave a marriage if your spouse is a danger to you or your children, but such cases do not give you a right to marry another person. "Now to the married I command, yet not I but the Lord: A wife is not to depart from her husband. But even if she does depart, let her remain unmarried or be reconciled to her husband. And a husband is not to divorce his wife" (I Corinthians 7:10-11). The only time remarriage is allowed is upon the death of the spouse (Romans 7:2-3), or if the divorce is because the husband is committing sexual sins (Matthew 19:9). Since that was the case here, you are committing adultery by taking another husband.
Since my ex-husband caused the death of the marriage and he was the man that separated us, am I still under the bonds of that marriage? Also, does his spiritual death count as once he was Christian and now he is an atheist?
And what shall I do with my current husband of three years?
Be silly and try to twist God's words all you want, but it doesn't change the truth. Marriages end when the spouse dies, not when the marriage dies. "For the woman who has a husband is bound by the law to her husband as long as he lives. But if the husband dies, she is released from the law of her husband. So then if, while her husband lives, she marries another man, she will be called an adulteress; but if her husband dies, she is free from that law, so that she is no adulteress, though she has married another man" (Romans 7:2-3).
And no, Christianity is not a requirement for a continuing marriage. "For the unbelieving husband is sanctified by the wife, and the unbelieving wife is sanctified by the husband; otherwise your children would be unclean, but now they are holy. But if the unbeliever departs, let him depart; a brother or a sister is not under bondage in such cases. But God has called us to peace" (I Corinthians 7:14-15). The last statement gives permission to let a marriage dissolve when an unbelieving spouse does not wish to stay, but it contains no permission for remarriage. Besides, you left him because you saw him as dangerous, not because he lost his faith in God. Now you are trying to say he is the one who left.
You freely entered into a covenant with your first husband. No one forced you. You did your own choosing, poor as you might now realize. Your choices came with responsibilities and consequences. You are committing adultery with the man you are currently living with. What you do about that depends on how much you want to live by God's standards.