Hello, my name is ***** ***** I will be the immigration attorney helping you today.
There is no exact gap period that you must remain outside the US when you leave. Usuallly you should spend at least a few months outside the US before you come back to the US for the full 6 months. If not you could be allowed back in but maybe not for full6 months. Since you have a child in the US on F1 visa then the CBP officers at the border should allow you back in the US more easily witout issues. Also you have the option to submit an extension for your B2 visa BEFORE January 10 2017. To get an extension you submit for I-539 and pay the fee and give the reasons why you want to stay. You can show that your child is on F1 visa and they should approve your application. They will give you up to 6 months and you can stay here in the US. Find I-539 here uscis.gov/forms
Good luck to you during this process and I hope this answer has helped you!
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