The book pictured was converted in Calibre with Remove spacing between paragraphs checked, everything checked in Filter Style Information, and 'body {orphans: 1; widows: 1}' added to the Extra CSS. I'm also using Caecilia font.
I changed the code to this and set a font for the footer since Caecilla was getting text cut off with a small padding on bottom.
Code:
#
# Example for AuraHD/H2O:
replace_string = D54355, `min-height: 70px;`, `min-height: 50px;`
replace_string = D54368, `max-height: 70px;`, `max-height: 50px;`
replace_string = D54385, `footerMargin: 40;`, `footerMargin: 20;`
replace_string = D5439F, `font-size: 16px;`, `font-size: 26px;`
replace_string = D543B1, `padding-bottom: 0px;`, `padding-bottom: 6px;`
replace_string = D543C7, `margin-top: 0px;`, `margin-top: 0px;`
#
# Uncomment one of the following if you wish the footer to use a fixed font.
# (And enable one of the Custom header style patches below using the same font.)
#
#replace_string = D543D9, `/*font-family:none;*/`, `font-family: Amasis;`
#replace_string = D543D9, `/*font-family:none;*/`, `font-family: Avenir;`
replace_string = D543D9, `/*font-family:none;*/`, `font-family: Georgia;`
#
When I completely disable the footer the text fills the screen how I think it should with footer, albeit with space for the footer.
edit: I also disabled all other patches but enabled `ePub adjustable top/bottom margin` (for fullscreen reading).