Hello and Thank You for using Just Answer. I am sorry to hear about the problems that you are having with your daughter. She is feeling very anxious about the negative feelings between you and your husband and especially needs to be comforted at night. She is afraid of many things because she has the fear of the unknown: especially the impending separation.
What you need to do now is to seek counseling for your daughter. Talk to her pediatrician to get a referrral for a child psychologist or counselor. She needs intervention and coping strategies in how to deal with her feelings of fear and what she needs to know about her parents.
Right now as her mom, do not worry about what her dad is or is not doing. You cannot control his issues and actions. What YOU can do is to continue to be as loving and as supportive as you can for your daughter. Comfort her when she is sad, lonely, and afraid. Praise her when she does something really well. Have as much fun with her as possible. She is still so young and needs to have the most happy and healthy childhood possible despite the family dynamics.
Have a great day!!!