I had a screamer like this. I stuck it out for two years and tried everything. Finally I just couldn't handle it anymore and termed. Neighbours I didn't even know previously were congratulating me
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I would say if you're stumped as to what to do and you can afford to, just term. Screaming is one of those things that makes your life difficult, but it also makes the other dc kids, your own kids, your husband, your dc parents, and your neighbours go bonkers too. If I had to deal with it again, I'd give it two weeks, and then term.