To the best of my knowledge, Calibri font is not (officially) available for Linux. There are only claimed metrics-compatible equivalent fonts, such as Google’s Carlito (see this question. Frequently, subtle differences in metrics remain in the table which result in the kind of behaviour you experience.
Check also that the replacement table in your Ubuntu does not force an alternate font for Calibri: see
Libre Office →
There is also a difference in the way Word and Writer define the page header/footer (if you have one). In Word, header and footer are located outside the page text area (inside the margins); while in Writer header and footer lie in the page text area (margins are just what they are: empty areas where nothing is laid out). This could result in expanding the LO document.
Have you tried the other way out? I.e. sending an .odt document to the Windows machine (Word undertands this format, at least if the document does not use advanced ODF features) and see if differences persist.
What you tell about the line of dots strongly suggests metrics problems between the font version (see my first point). To avoid this, I usually set atab stop to the position where I want the leading line to end, so that I control accurately the position (it will no longer depend on character width). In the
Tabs tab of the paragraph style, you choose the fill character for the leading. Use a period in your case, but you can also use an underscore to get a continuous line.
A word of caveat: if you choose the “tab-with-fill-character” solution, you better define specific paragraph styles so that you don’t mess the layout for "standard paragraphs. At least one style is needed if you can manage your manual entry paragraphs to look the same.
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