Look through your list of installed programs, and see if there are any extraneous programs you can uninstall.
Download CCleaner, and run both the regular cleaner and the registry cleaner.
Disable all anti-virus and security programs while you game. They won't do you any good, and will hammer your already weak and underperforming CPU.
Defrag your HDD and trim your SSD. You can use Windows' built in drive optimization tool to accomplish this.
Disable Windows Aero while gaming...?
Move your Windows pagefile from your SSD to your HDD to increase your SSD's lifespan, and reduce the frequency at which you must trim the poor sucker.
Download Guru DDU or whatever it's called now (Display Driver Uninstaller) to completely and utterly wipe all display drivers from your drive. Then reinstall just the latest one to make sure there aren't driver conflicts causing the decrease in fps.
There are ways to optimize the OS by doing things like disabling services that don't do anything for the average gamer, like virtualization and server encryption. I don't know any off the top of my head, since I googled this and just tried everything out, kept what worked, and reverted what didn't. Don't go raising the priority in task manager though, it causes plenty of stability issues that are more headache and actually decrease in-game performance.
You may have to do some, I mean a lot, of UserOptions.ini editing to get higher framerates with an FX8350. You might have to limit yourself to CQB on completely potato graphics if your framerates are uncooperative. I bet, the green miasma is really hurting your fps. (I don't play H1Z1, I've seen gameplay of it though.)
Knowing that H1Z1 and Planetside 2 are derivatives based on the same engine, and being a PS2 vet myself, I know first hand how bad framerates can be with FX CPU's. With the same settings and everything except MB and CPU, the difference between an FX8320 at 5.2ghz and my current i5 4460 under similar combat conditions (250+ people with artillery firing from all sides, and Papa Vanu's ground pounding platoon flying above) was the difference between 15 fps with frequent dips into the unholy territory of 5spf, and 85+ fps stable. It's the difference between ragequitting, and being able to enjoy the farm with adaptive vsync keeping everything buttery smooth all the time. I won't even go into how bad it was back when I tried to run PS2 with an Athlon 760k, even at 4.9ghz. Oh the horror, oh the nightmares...