Your last paragraph really hit home with me. I too had become distant with my W and relationship with God (even though I didn't know it at the time). My W left in mid-Novemenber (told me she was leaving in early Nov).
I often prayed to be a better H and step-father but didn't feel I was getting better. Her leaving made my eyes open very wide; not only to her but to renewing my relationship with God.
I hope I am fortunate enough to receive the same opprounity that you have. Prayer is very powerful; keep praying for the wisdom and strength to renew your marriage and relationship with God.
