Questions about changing "Simply Read" theme

I recently changed my theme to Simply Read. I love the clean layout of the front page, but the post page is not very appealing. How can I change the fonts and adjust the width of the text (I’d rather have it all centered in the middle of the page then have it on the left)?

Also, I prefer the Jetpack Related Posts feature than the one embedded in Simply Read. How can I get rid of the Simply Read Related Posts?

Thanks!