Hi, I'd like to help you with your question.
When it comes to adulterous relationships, the real reason behind committing adultery needs to be addressed before you marry the person you are with. You may have heard people say that "once a cheater, always a cheater". Well, that is true, to an extent. I say that because most people who cheat are doing it because of something within themselves, not their marriages. Even if their marriages are difficult (which is hard to prove), they have many options in resolving the problems. But instead of resolving them, they cheat. When a person cheats, they are usually thinking only of their own feelings and are not concerned with fixing the marriage. They may have made an attempt, but for some reason they chose not to follow through and end up cheating instead. So in essence, when the marriage breaks down, they choose to cheat.
When you are considering marrying your boyfriend, you need to consider how he reacts to difficulties and problems. When he was unhappy with his marriage, he came to you. When he lost his job, he went home. Although there is nothing wrong with going home when you lose your job, you need to consider his ability to stick it out with you and if he would stay around should other bad things happen.
Since he has not contacted you much since he went back, you should also consider that as well. How does he treat you when you have needs? Is he consistent and reliable? Does he put you first? Those are some questions to ask yourself.
If you do choose to stay with him and marry him, you may want to consider pre marital counseling to help him work through the issues of divorce and adultery so you can start your marriage with a clean slate. To find a therapist, talk with your doctor for a referral. Or if you attend church, your pastor could help. You can also search on line at http://therapists.psychologytoday.com/rms/.
Here are some other resources to help you:
1001 Questions to Ask Before You Get Married by Monica Mendez Leahy
Don't You Dare Get Married Until You Read This! The Book of Questions for Couples by Corey Donaldson
Things I Wish I'd Known Before We Got Married by Gary Chapman
You can find these on Amazon.com or your local library may have them for you.
I hope this has helped you,