First off: Your total used RAM is only 23.6% of the 1GB available. The rest of the RAM is stored in cache, but this keeps it as still being available.
The reason why the swap isn't being used is because the server doesn't need to use it. If your server is swapping, often, that's a very bad thing. Swapping takes much longer to process than accessing physical RAM (RAM runs at anywhere from 8GB/s to 32GB/s depending on your system while swap, being on the hard drive, goes about 80 MB/s). So the fact that your server is swapping to little is, in fact, a GOOD thing.
As for why the server is slow, you have no provided enough information. Could you please print the top lines of "top" so that we can see CPU usage, etc?
Also, you could download and install sysstat which can show you how active your CPU's and hard disks are. If you download that and install it, print us out the following:
Edit: Looking at your third image, I see that your system has swapped 120MB or so. Do you run MySQL on this server and access some medium-sized databases? If so, MySQL might be trying to allocate more RAM than the server has available thus causing short but often swapping.
You need to check the configuration of the server and the control panel that you have installed on the server. Also you need to check if the firewall on the server is properly configured, so that the memory usage of your server is limited.
A site with 30000 hits on a single day is going to take a lot of memory on the server. But it also depends on the size of the domain, that is the disk space allocated to your domain and the disk usage of that domain. If the pages of that domain is using heavy diskspace then the that site would consume a lot of bandwidth.
Well, if the memory allocated to your server is consumed, the swap memory is automatically used and if it doesn't then it means that the server is not configured properly.
You can't determine memory usage based on the number of pageviews a website gets. So stating "A site with 30000 hits on a single day is going to take a lot of memory on the server" is a completely premature statement with no basis in reality. Also, the firewall and bandwidth have absolutely nothing to do with the amount of memory a system uses.
To support my statements:
I've managed servers with sites that get over 22,000,000 pageviews per day that use less than a gig of RAM. At the same time, I've seen sites with 300,000 pageviews per day which use over 4GB of RAM. In fact, I work with sites like that on a daily basis.
The type of content being served greatly determines the amount of RAM a site will use. Static content will use almost no RAM. Light MySQL usage will also use almost no RAM. Any amount of MySQL usage that scans over a large number of rows will use an increased amount of RAM. Scan over a MySQL table that has a hundred thousand or more rows and you could start seeing issues with RAM if there isn't enough. Scan over the same number of rows at a constant rate (say once per second or more), and you'll see a slow-down. Finally, scan over a MySQL table and return a large amount of data, and you'll have the same effect as if you were going over hundreds of thousands of rows.