Your wife may have been getting ready to go into full blown mlc. Generally a year or more pre-crisis, they begin to withdraw, become snippy/picky and yes, the sex drive can be reduced. It's because they are feeling that something is different within themselves and they don't know why they are feeling doubtful, curious and yes, depressed.
Please keep in mind that dbing is for YOU. It is a tool to help you manage and try to find a way in which to deal w/the situation. It is also a tool that can be used in your day-to-day life to help you communicate and manage your life in a diffeent way. If you feel that you don't agree w/your wife about something such as the children and/or finances, then step up to the plate and discuss it w/her, but do it in a calm and collective manner. Leave the emotions out of it.
Well, my friend, you are going to have to dig for more patience because you may not get that "love and affection" that you so need right now from her. She doesn't feel the same way about you and the marriage right now and it may take a long time before those feelings return. You can't force her to change, you can't control her or the outcome of her crisis. You can't push or you'll see her run the other way faster than a speeding bullet.
Stop doing things for her. She needs to face the consequences of her actions. Do things for you and your children. Leave her be and live your life as if she were a roommate for now. Learn to do things on your own and w/your children. When your wife begins to sense that you are happy and living your life, she just may become curious enough to ask questions and want to partiicipate in some family events.
Sit quietly, the answers will come. Be patient and when you can't be, walk away or come here to vent. This is not a sprint, but a marathon and it will not end any time soon. This is a long journey for both of you.
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.