Don't know where to go from now...

I'm really confused and don't know what to do with my life now. I have two mayor issues right now. 1. I got divorced 2 months ago (we had been separated since November Las year). My ex is a good man and we had an ok relationship, except that there was no intimacy at all between us. We were like roommates; by the time be divorced we hadn't have sex in 4 years. We were married 7 years. I left my country and my career to be with him. Living with him wasn't bad, but we simply weren't happy. Problem is now he's asking me for an opportunity to be together again. He has promised to help me achieve my goals and promised to be more passionate and show me his love. We have a 3 year old daughter and she is so happy when the three of us are together. I feel guilty for taking her family from her. Should I give him an opportunity? Would he change for real and be more passionate about us and help me achieve my goals now that he knows I can leave him? 2. During the process of my divorce my "bestfriend" led me on to think that he had been in love with me for all the time we had been friends (15 years approx). He told me so many lies about how much he loved and cared for me just to dump me after we had sex (this was after I separated, just 3 weeks ago). I don't want him back, but I just can't get over the fact he did that to me. I'm really hurt and full of resentment, can't stop thinking about it. I feel stupid for believing him. How do I get over all this??