To make the images larges relative to the text, try increasing the 'Zoom (dpi)' setting in the bottom menu, 3rd tab (page icon).
To left align just the body text, a custom style tweak may work for your book. First try the following tweak, which should only left-align paragraph text:
Code:
p { text-align: left !important; }
(Go to the Style tweaks menu, uncheck your current text alignment selections, then long-press on 'Book-specific tweak' and enter the above line.)
If that doesn't work, you may need to investigate further. Select some text on a page that encompasses both some body text and a little divider image (e.g., from Yes I do." to Holden), and on the pop-up menu select 'View HTML' Then take note under what tag either one is. (If unsure, you can copy and paste the text or a screenshot here.)
For your style tweak to work, the little image must be under a different HTML tag than the body text.