[mothered]

what do you mean, for the moment, she basically decides if he's allowed to see his kids or not

Precisely what I'm referring to by this:

not allow her to dictate what he can/cannot do with his very own children.

"He" needs to take control and do whatever It takes (legally or otherwise) and decide when "he" can see his children. I've been there, done that and whilst It's not easy by any means, any given situation can change- but only If "you" decide to apply yourself and take control of the matter.