You cannot force detachment. It will come naturally as you walk your path. As for stop loving someone, detaching isn't about that at all. It's about helping you find a way not to react to what someone says or does. You love this person w/your entire being and it is so difficult to see them struggling and behaving in a way that is so foreign to you at the moment. You can still love them, but not like the behaviors. Lovingly let go a bit, or as we tend to say around here, drop the rope, do not hold on too tight.
It's okay to cry. Crying helps you relieve the stress and hurt of what is happening, but it also will help you become stronger in time. You are human and you've been hurt terribly and it is understandable that you are going to have period of deep, dark despair. Do not be ashamed of breaking down. Sometimes we have to do this and then you need allow those feelings to wash over you and release them.
Try to keep the focus on you and your children. They need you now more than ever. Please take care of yourself.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.