Child support and going after more canada

The father pays child support monthly and has for 10 years. The child is 11 turning 12. The parents never went to court, they did mediation with no set custody agreement but the father is active in child's life (40/60 custody) based off his income he paid $500 monthly that they decided on together as that's what typically the amount is based off income (basic job, 23 dollars an hour) the mother never took the father's tax information to update yearly and the father never asked

He now makes $25 an hour with another child (different mom) that he fully financially supports. The mother of the 11 year old child is saying she's going through fro and going to screw him on all previous tax years from the last 10 years and he will be paying her a shit load of money.. she's withhold the child because she's mad at fathers partner and demands an apology over something that never happened and if she doesn't get the apology the father can't see his son and she will do everything to fuck him financially and take him to the ground.

Can she really do this? I know it's alot of drama and the father knows he needs to seek legal help and get a lawyer to go to court for a real agreement on when he can have his son so she can't pull this shit.. he pays her money is a great father always wanting to spend time with his son, goes an extra mile to help out has done nothing but be nice to this women.. when her car broke he drove her places, when her tired were slashed by her ex he drove her to the machenic, when her and her ex got into multiple physical fights and cops were involved he showed up to pick them up, she needed extra money or money early he paid, he paid her cellphone plan ontop of support for 4 years... he does it all... and there's enough deat beats out there like why does she act like that's what it is? Why isn't she happy that this man wants to be involved with his child and would do anything for him?? Its like she wishes he was a deadbeat that she tries to make shit up and start huge fights using their son as a pawn to try to get him to go off on her. It's fucking ridiculous, he's so easy to deal with...