I've had instances of my Mac running slow. However it's usually caused by CPU hogging apps running in the background. And judging by the report it says you have a LOT of them running, hence it's running very slow. It doesn't help by having only 8GB of memory... near the end of the log it says you have 2.45GB of free RAM left!
Rather than getting an SSD drive, first upgrade your RAM (memory) to 16GB, if that is possible for your iMac - that should be your top priority upgrade. Then the SSD drive.
Also, I suggest you load up an Apple program called 'Activity Monitor' (comes with MacOS), and see what programs are using '%CPU', which should be the second column in the list. Note most apps take up nothing at all, most of the time.
If the program is taking up 50-90% of CPU time, then that is the culprit.
Try booting in safe mode, run a virus check first, then disable as many background applications as possible.