Given his relationship with Drexel who was a proud groomer that bragged about it, his relationship with Vito an open pedophile and his relationship with Melton a man that takes joy in saying he will rape other men's children and the fact he walked back his position on stuff like cuties
I would not bet money on Nick sexually abusing any of his kids on top of neglecting them. However I also wouldn't bet money against it, every time I've ever given him a benefit of the doubt over the years it's always turned out wrong.
Also his obsession with novel sexual experiences with any person but his wife and his need to control and trick people the easiest people to trick, control and push to get what you want from are your own children.