FAS in children.

My partner has full custody of his kids, the mother isn’t allowed to see them. Court ordered. She drank with two of her pregnancies which resulted in two children being FAS. They were diagnosed at 4 years old, apparently they can’t properly give a diagnosis until that age but it was expected prior that they were. My partner had no idea she drank with the first child who has FAS & the child came out completely normal (no signs or anything of any problems) but noticed behaviour as the child left infant stage. He caught her drinking with the second child diagnosed with FAS, he would smash bottles of booze, he opened a new bank account so she couldn’t access money to spend on booze but she found ways to get it (stealing, cashing empty check envelopes at the bank for immediate cash, selling items in the house & even started doing sexual favours for people to purchase alcohol or receive it for free) once the second child was born, he took both kids and left. Was in a shelter because he lost his job due to no one able to watch the kids while he worked. He worked hard to get stable and provide a proper home environment for his kids and proved she was unfit and unable to properly care for these kids. He knew deep down that they would suffer the consequences of their moms poor choices but wouldn’t change having them as they’re his world. They’re great kids! Super sweet, quirky and awesome little humans but they can be a lot of work. It’s 24/7, 7 days a week and I can see he gets exhausted and overwhelmed sometimes… they constantly need eyes on them (like most kids but this is extreme) they want to get their hands on everything and break it. They destroy their rooms, break dressers, rip up mattresses, break toys, shit and smear it. It’s chaos sometimes, we sit outside their doors when it’s bedtime to make sure they aren’t doing these things as they can be very discreet about it. We don’t leave them in their rooms, when they wake they come out so it’s not like they’re stuck in their for extended periods of time, just for sleeping. They don’t listen, they don’t understand consequences or care about what they do that’s so very bad… they’re old enough to understand and I’m not sure if it’s because of the FAS that they just don’t get it. We’ve tried every form of discipline (other then abuse obviously) we try talking calm and going on with the day. We have done time outs, taking things away, being firm (stern voice) and even tried ignoring bad behaviour (possibly them seeking negative attention) we don’t give them much sugar (they have a diet we follow that was suggested by a doctor). I am looking for other moms or people who are familiar with FAS or has a child in their home whose diagnosed and what behaviours are normal for fas, other things to look out for, approaches I can try to help make the days a little less stressful for everyone and hopefully some insight from someone whose experiences this first hand. Thanks