Hi there – I’ll answer your questions separately here.
Should I start another post for each of my new questions?
For new questions, please start a new thread. It’s not necessary to make a new thread for every single question, but it’s good to try to stick to a couple per thread.
with the custom CSS i can essentially make this theme look anyway I want?
CSS can do a lot to change the look and feel of your site if you’re comfortable with it or willing to learn! Larger changes, and those related to functionality, can be made in child theme instead.
Learning how to target your site’s CSS will help you make certain design and layout changes. Here are some very helpful posts that will help you customize your site with CSS:
An Intro to CSS: Finding CSS Selectors
An Intro to CSS, or How to Make Things Look Like You Like
Intro to CSS: Previewing Changes with the Matched Rule Pane
How to Find Your Theme’s CSS
https://thewc.co/articles/view/web-inspector-tutorial
https://cssworkshop.wordpress.com/
If CSS is new to you, here are some resources for learning more about it:
When changing positioning with CSS, be sure to consider and test smaller screens. If you decide to restrict your changes to certain screen sizes, you can learn more about using media queries that target certain screen sizes here:
Using Media Queries with Custom CSS
Media Queries for Standard Devices
http://webdesignerwall.com/tutorials/responsive-design-with-css3-media-queries