Formatting a manuscript for Amazon KDP paperback

I need someone with a high level of skill in formatting. I have my formatting complete (Chapter Headings, page headers, margins arranged to satisfy KDP); however, the last line of many pages is short, even though it is not the end of a paragraph. Also, the justify right command leaves many lines throughout the manuscript with too much space between letters. I find no way to correct these problems. I'd like this manuscript to be as close to perfect as possible.

If you understand the problems I describe, and you know how to correct them, send me an estimate. All corrections must leave text within same margins that are already set.