If your site is serving a lot of traffic then it will use a lot of resources regardless of theme used, you will need to upgrade your hosting if you are experiencing high server usage. The size of above resources are 4KB and 89KB only.
In shared hosting:
One 4 core cpu is shared with 100’s of websites
In VPS: it is shared with 12-20 websites
In Dedicated: your site has full access to all server resources
When I visited your site, it was very fast and quick to load already.
To disable xmlrpc you can use the following plugin