There are no pages in a Word document. Documents are made up of several layers, a bit like a pile of transparencies that go to make up the whole. The main body text is a complete block of text that flows between the current margins. This is why your attempts to split the document by page are running into so much difficulty. If however this is a document created by mail merge - see
https://www.gmayor.com/MergeAndSplit.htm