OK Rachel
I see nothing amiss in your system, but I would say that mesh is slower to rez for me too on 5.0.7 but the symptoms you are reporting sound more like a problem with the simulator/region you are in.
Or:
Your graphics system is not great the x30M GPU is a weak one (the second digit (3) is the important one really together with the M suffix), especially with a 240m draw distance. Try reducing it to 160 or even 96m see if anything improves. I find LOD of 3.5 works better for me with mesh especially.
I am guessing that you have a dual graphics set up from the Windows graphics driver listed...make sure that Firestorm IS using the Nvidia GPU and hasn't reverted to the on-board graphics of the CPU after a Windows update (it can happen).
Some of your symptoms suggest your PC is also running slowly...time for a scan perhaps?
Outside of this, are you WiFi or hard-wired? If you are WiFi, a bandwidth of 1450kbps is way too high. It needs to be around 500 kbps for WiFi. Check and reboot your router. The reason for a low bandwidth requirement for SL is due to the slow packet delivery capability of all WiFi systems (I was told this by someone who ought to know, an ISP engineer).