http://www.goingtojesus.com/site/php/books.php?tname=marriage:2
1_Name: Tracey
3_Comments: My wife and I are Christians. 3 years ago, my wife committed adultery. I chose to forgive her and attempt to salvage our marriage. 5 months ago, she stopped wearing her wedding ring and stated she did not want the marriage. She has now filed for divorce. The disturbing part is that she sings in the choir and goes to bible study regularly while clearly making a decision that is unscriptual. She states that she is just willing to be alone for the rest of her life which is clearly not the truth. Although there is no proof, it appears that she has been having another affair and has definitely been communicating with a leader in our church. I discovered they had been secretly communicating for 3 months. Likely that they are now. Spoke with the pastor on two occassions about their communicating, he refused to speak with them. I no longer attend that church.
With that brief summary which does not give you all of the details. There is so much more. My wife appears to be willfully divorcing unscriptually. It appears she is being openly defiant to God. It is really disturbing and scary to me that she has gone to this point. We have two young daughters. I have done all that I could possibly do to save it.
1) Do I have scriptual grounds for divorce? 1 Cor 7:15 or Matt 19:9?
None of the counsel contained in the Scriptures applies to either of you unless you are born of the Spirit. I will proceed, on the assumption that you both have been born again.
http://www.goingtojesus.com/topic_newbirth.html
Under normal circumstances, the answer to your question is yes. But you living with her for this long after the infidelity complicates matters. Of course, her demanding a divorce again now comes into play. My guess is that if she divorces you, it will not be long before she commits the act again that provided you the original grounds to end your responsibility to the marriage — even if she is not doing that now.
2) Is my wife although a Christian an unbeliever?
Being a Christian has nothing whatsoever with being a believer or being an unbeliever. The issue is, has she been born again. That is, has she received the holy ghost baptism? and have you?
3) Must I have photos, video or a confession from her that she has had another affair to divorce her for the suspected adultery?
Suspicion is not grounds for divorce and re-marriage. But according to Paul, in 1Corinthians 7, believers are free to separate at any time, for whatever reasons that seem to them to be good, but they may not re-marry.
4) If the divorce continues am I able to remarry?
Under the conditions I mentioned above, in my reply to your first question, absolutely yes.