Everyone has given you great advice. I usually step away from DV posts because of what it triggers in me (a child who grew up in a dv house).
But you are very smart and clearly have goals to better your life so I wanted to respond.....
Something I tell the mom's I work with who are in your situation is that (at least here in California) if two adults are fighting (even just yelling) is considered child abuse by CPS-- because of what kids like me saw and how it affects us the rest of our lives, there is validity to the reasoning behind this.
I wasn't clear if he cut your son's ear or his own? If it was your son's and he didn't allow you to take him to the ER, that is a very serious thing as well.
I have worked with mom's who have been doubly traumatized: first by the abuse, then by the possibility that they can have a situation with CPS.
I know it is horrible to think about but I can tell you as a child who witnessed things, please please have a plan to keep yourself and your child safe.