I think we're putting the cart before the horse here discussing how mom should file for support when she's not the custodial parent - neither before nor after the child "becomes school age," whenever that is determined to be. She needs to sort that issue out first. No one has asked whether she is paying support to dad.
Honestly, it doesn't seem like either of these parents want the child that much. I'm not convinced a judge would or would not change custody given mom's attitude and dad's as mom has presented it. I wonder what dad's side of the story is here.

