Welcome to the family wvgal!
We're glad you found us. It's a little quiet here today, but it is pretty active during the week. Keep coming back and read and post as much as needed.
My children are teens, so I gave more information than you will need for your son. I suggest you keep it simple. Mom and Dad are living apart for a while. Mom and Dad still love you very much. (reinforce that he did not do anything to cause the breakup) His young world is in the moment. His concept of time is not fine tuned like ours. He doesn't yet understand weeks, weekends, months, etc. He just knows today Dad is not at home.
Are you getting help for you? You will find lots of information and support here for yourself.
You are a good mom! You have removed the drama from your home and you are creating a safe environment for you and your child. Good on you.
You and your son deserve time to create a normal schedule for yourselves. You can decide how often your son visits his dad and when. You can say no to keeping your son out of school.
No. It's a complete answer.