No, your refund will not be seized for your spouse's back child support, since you filed married filing separately. But if you lived with your spouse during the last six months of 2017 you are not allowed to file as Head of Household. You could file as married filing separately and claim the children, etc.
Am I Head of Household?
https://ttlc.intuit.com/questions/1894553-do-i-qualify-for-head-of-household
https://ttlc.intuit.com/questions/2900097-what-is-a-qualifying-person-for-head-of-household
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
