Assault Charge With No Lawyer

My son was arrested for domestic violence last month. He went before the judge and entered a plea of guilty.
When the situation was described, the judge said that it could be a self defense case and the judge entered a plea of not guilty for my son even though he plead guilty, and gave him the choice of paying 5,000 bail or spending the month in jail until his court date.

My son's girlfriend phone the prosecuting attorney and asked what she needs to do in order to have the charges dropped. The PA told her that she can't really drop the charges, but that my son can plead
"guilty under advisement"

And will probably pay a fine and have to attend anger management.
My son does NOT have a lawyer and we are unsure how he should plead.
I am concerned that if he does not handle this the right way, he will be sent to jail, or be jailed because of the inability to pay high fines or both.

What happened: My son and his girlfriend were having an argument that got out of hand. His girlfriend tried to hit him between the legs and he pushed her down and then kicked her in the butt.
My son acknowledges the fact that she is no threat to him physically, but he did push her when she tried to hit him, and then he kicked her in the behind because he was angry that she tried to hit him there. He acknowledges that kicking her was inappropriate and unnecessary.

The charge on the bond release paper says .. "cruelty to spouse/non-violent"

Can anyone offer some advice how he should handle this in court?
My son is 21 yrs. old and has no history of assault.

Michigan Mom

Having a plea taken under advisement is not all bad - it would allow him to avoid a conviction. But if he has similar difficulty entering a plea, such that the court won't accept his allocution as the basis for a finding of guilt, then court may order him to go to trial. Some counties have very stringent domestic violence policies. Your son would benefit from consulting a criminal defense lawyer.