Hello There,
Thanks for writing in!
1.) Please change the font size in the theme options. Go to Pro > Launch > Options > Typography and adjust the font size of your Body and Content > Content Font Size.
2.) To make sure that you feature image will have the same width as your post content, please add the following CSS code in the X > Launch > Theme Options > Global CSS (http://prntscr.com/evui3r)
.single-post .entry-featured {
max-width: 844px;
margin-left: auto;
margin-right: auto;
}
And also I noticed that you are using an older version of the theme. Pro 1.2.7 is now available in automatic updates! This release contains fixes for several issues so be sure to check out the changelog (https://theme.co/changelog/). After doing the updates, always remember to clear all caches when updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
Please let us know how it goes.