The judge is unlikely to rule in your favor simply because of a typo. If the answer was filed within the 5 day period, it will likely be fine. Judges tend to be a little less... judgmental... with pro se litigants when it comes to these things.
You will need evidence to show that he knew he was to pay rent, or that he did pay half as agreed at one time. He may know that he was to pay 1/2 of everything, but he may not admit to it. Do you have paperwork showing this? Receipts or did he pay in cash? Emails evidencing that he knew he was to pay rent? Facebook? Texts?
If you cannot prove he was a tenant, he has a defense against an eviction. You may have had to file an action for unlawful detainer.
I recommend you set up a consultation with a landlord / tenant attorney. A lot of them are free, and while it may be expensive to hire the attorney in the short term, imagine living with your ex for another 6 months while you figure things out.
Best of luck.
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