Hi,
To improve the pingdomtools even more you can use a CDN and static files will be served from a cookiesless domain. Now you are serving them from the same domain where wordpress is installed and wordpress use cookies.
I don’t think currently there is an option to remove query strings from static files.
94 as grade is not bad at all. The 17 seconds to load are bad and that is probably due to a underpowered server for that many listings.
If that is a shared server, that’s why it loads so slow. Shared server are barely enough for blogs and static websites, definitely not for applications.
What kind of hosting plan is that and where is it located? Because from my location (central america) the website loads faster then 17secs.
If your target audience is in Europe, you should make sure the server is in Europe, not Canada.
Thanks