I just found out yesterday Google has a PageSpeed add-on for browsers that I'll suggest using as it breaks down performance issues by prioritizing importance. It also works in the browser (Chrome or Firefox) as an add-on. It also explains problems and solutions more if you're unsure what each item really means.
I ran PageSpeed on your site and my suspicions on the images being unoptimized were confirmed and it was the number one thing listed. Once fully optimized, it says you can reduce your image sizes by 43% (over 1.5MB). You can learn more about it on best practices page that talks about optimizing images.
Some other major things you can do are Gzipping your content (don't gzip images, though). This can save you half a MB almost. You may encounter problems with the PageSpeed website confirming your files are gzipped, but the website I linked and the PageSpeed add-on may work better for you.
It also says your images are too large for the size you're using them. This can save you ~.25MB.
There's more suggestions by PageSpeed but these should lower your page size significantly.
I'd also recommend double checking how your caching plugin works as PageSpeed also suggests to add expiration headers to some files (it's easy if you have access to your .htaccess file).
Overall, get PageSpeed or YSlow for your browser. They'll tell you similar things (I just have a preference for the former as it works in Chrome's developer tools panel.)