What if I am divorced but not for “acceptable reasons?” Do I need to remain unmarried?

If your former spouse is married, I believe it is acceptable to marry again. However, if they are not remarried, your focus should be to restore the full measure of the covenant relationship that you took an oath to uphold. Again, you are still married to that person in the eyes of God:

… from the beginning of creation, ‘God made them male and female.’ 7 ‘Therefore a man shall leave his father and mother and hold fast to his wife, 8 and the two shall become one flesh.’ So they are no longer two but one flesh. 9 What therefore God has joined together, let not man separate.” Mark 10:6-9

Again, if your “former” spouse is unmarried (yet you are divorced in the eyes of the law), you are still married to that person according to God and should pursue reconciliation. You have no Biblical basis to get remarried since your spouse is still living and unmarried. Therefore, repent of your actions and pursue reconciliation in obedience to the Lordship of Jesus Christ.

What should a person do who is married to an unbeliever who refuses to be faithful to the marriage covenant? Should they stay for the sake of the Gospel or are they free to remarry?

No. You are free to remarry unless you feel convicted by God to stay in the marriage in an effort to save it. The unfaithful spouse has broken the marriage covenant and you can (but not “must”) divorce him or her on this basis. We should note that this outcome is not God’s best, it is only a concession given due to the determined unfaithful actions of the spouse.

Jesus grants a person a basis of divorce due to marital infidelity:

… I say to you that everyone who divorces his wife, except on the ground of sexual immorality, makes her commit adultery, and whoever marries a divorced woman commits adultery. Matthew 5:31-32

Paul’s words are instructive in regard to our ultimate desire for peace if a spouse (who refuses to stay faithful or simply desires to divorce) their, now Christian, spouse:

… if the unbelieving partner separates, let it be so. In such cases the brother or sister is not enslaved. God has called you to peace. I Cor. 7:15

How long should a person (who divorced due to the unfaithfulness of their spouse) remain unmarried in the hopes that there spouse would repent and seek to reconcile?

As long as they believe that is what God wants for them. If you choose to begin dating, it should go without saying that the new person in your life should be a growing follower of Jesus Christ. It would also be wise to seek the counsel of the pastors of the church as well as godly friends. All relationships should be centered on the Lordship of Jesus Christ in an effort to spread the fame of God through the pattern of making disciples that our Lord gave us. During times of emotional upheaval, that goal can be difficult to discern or fully apprehend. Therefore, having other wade into one’s life for the express purpose of helping develop Biblical and thoughtful patterns in “dating” again would be wise.

If a spouse has been unfaithful due to lust via the internet or other media does that qualify within the boundary of the “exception clause” of Matthew 5:31-32, Matthew 19:9?

No. The actions of the sinning spouse are sinful and wrong, but they do not serve as the basis for divorce at this level. Let’s quickly examine why this is so. Jesus said:

“You have heard that it was said, ‘You shall not commit adultery.’ 28 But I say to you that everyone who looks at a woman with lustful intent has already committed adultery (GK. “moicheuo”) with her in his heart. Matthew 5:27-28

I do not believe lust via the internet qualifies given the clarification the Apostle Paul gives to this type of unfaithfulness in I Corinthians 6:15:

Do you not know that your bodies are members of Christ? Shall I then take the members of Christ and make them members of a prostitute? Never! 16 Or do you not know that he who is joined to a prostitute becomes one body with her? For, as it is written, “The two will become one flesh.” 17 But he who is joined to the Lord becomes one spirit with him. 18 Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body. 19 Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, 20 for you were bought with a price. So glorify God in your body.

The clear expression of unfaithfulness to one’s vows of purity in marriage seem to directly relate to another person and the physical violation that adultery brings. I am not saying it is not sinful and needing to be dealt with, I am saying that this sinful action does not qualify as the basis for a Biblical divorce. As in all failings, the couple should pursue reconciliation via the help of spiritual leadership (Gal. 6:1-2) and the help of the church as necessary (Matthew 18:15-22).

Can a Christian, who was divorced for the wrong reasons, remarry if that divorce occurred prior to them becoming a Christian or is he or she in a continual state of adultery and therefore prohibited to marry?

No.

The Apostle Paul tells us:

For the love of Christ controls us, because we have concluded this: that one has died for all, therefore all have died; 15 and he died for all, that those who live might no longer live for themselves but for him who for their sake died and was raised. 16 From now on, therefore, we regard no one according to the flesh. Even though we once regarded Christ according to the flesh, we regard him thus no longer. 17 Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come. 2 Cor. 5: 14

The sins of the past are covered through the payment of Jesus, accepted by God, on the cross for your sins. Rejoice in that truth and “go and sin no more.”