How do I reasociate AllItems.aspx with default discussion board views (Subject, Flat, etc,,,)?

While attempting to modify the default Subject view to add a custom column I used SP Designer 2013 to copy AllItems.aspx code (cut/paste) into a custom view (Subject1.aspx). When I saved Subject1.aspx SP disassociated all views from AllItems.aspx and replaced with Subject1.aspx. It also removed the default Subject view (Show in "Top-Level") and replaced with Subject1 (Show in "All"). The original AllItems.aspx file still exists on the server.

I also seem to have corrupted the default Flat view where it will not show any discussions. So I need to restore that also.

How can I resolve this. I have attempted to create a new discussion board but cannot move the original content to the new board. I do not have access to Visual Studio so I am limited to powershell. If there is a powershell way to move discussion topics and items I would move the content to the new discussion board, delete the old discussion board, and rename the new board. Is this possible?