Well, you simply have to go back and delete the page breaks in those instances. If you are wanting the chapter headings to all appear at the top of the page then, if anywhere, you would put a page break following the headings. However, I would assume you would have some sort of text following the chapter heading so am not so sure if I answered you correctly or not.

I am not familiar with kindle or how it interacts with word so I cannot help you there.