Would like to rewrite the SBT theme so it is faster and easier to maintain in the future.

Let's stay with the same design and site layout.  We don't want to change that right now, because we don't want to hurt our search results.  

We just want to get rid of bloated code.  Make it a more efficient and faster loading site wherever possible.

Also,  I just saw this article that talks about speeding up WordPress sites.  Maybe there are some things they did that we can do. For instance, they talk about image optimization. 

https://nickleroy.com/blog-posts/wordpress-site-speed/