I had this wonderful, thoughtful long reply, then the computer ate it!
So the jist of it: I'm very sorry about your husband leaving. It must be difficult on you. I'm sure that the girls are sensing your growing anxiety and that is why it is getting more difficult to say goodbye.
About school, I've been in college for 10 years, and in that time, I have come to realize that most professors have a great understanding for what it is like to be an adult trying to get higher education. Talk to your professors and let them know what is going on in your life. Who knows, they may be willing to let you get out of some of your hours by writing a paper or doing an extra project. Most professors are willing to work with you in order to help you complete the course.
Most of all, take care of yourself. Take the time to do special things for you (like your haircut and color) You need to be in your best mental state for your family. Good luck. You and your family are in my thoughts and prayers.