It certainly would be more difficult for Mike to run off and marry someone else on a whim had you been married, but aside from that, I don't know what could have stopped him.
To some people, marriage is nothing more than a piece of paper that can be reversed. It's so important to identify WHY you want to be married...and probably pretty important that the two reasons match.
Sorry...I know I'm not answering your questions. I don't think I can. Will he come back? Who knows. Statistics? I don't know, but also don't know if it really matters what happened to other people. Most people in this forum believe that living together before marriage is a recipe for disaster, so it might be difficult to get much information about statistics on this type of thing.
If I were you, I'd focus on what you can do to bring him back to your family if that is what your goal is. You basically need to decide to go on with life without him (working with him regarding his parental role for your daughter), or try to attract him back in an honest and loving way. If you can get him back, marriage really should be discussed. If he cannot commit to marriage, he probably cannot commit to staying with you and your daughter and you're probably setting yourself up for more misery.
The Harley concepts are designed for married couples, but are very useful for any longterm relationship. Read up on it. Maybe post your question in a forum with more traffic. I started asking my premarital questions here, but quickly moved to the Emotional Needs forum because not many people post here.
Btw, messages like the one posted by hamincold are pretty much frowned upon here. This poster is new and may not realize this. This forum is pro-marriage...or in our case, pro-relationship. People who cannot support that perspective are missing the point of this web site. Cnf, I recommend posting in the EN forum...I think you'll get many more responses.
Hang in there.
Smile