i agree with others that until his home is at least habitable the children are not to be over there and absolutely NO overnights. he is allowed to live in squalor if he chooses, but that is not adequate for children.
it is also NOT OK for him to "borrow" from his children's savings accounts! you probably won't see that money again. close that accout and open one that does not give him access.
i wish you and your children the very best in your new home!