I would start by checking the systems firmware. Follow this Apple T/N: About EFI and SMC firmware updates for Intel-based Mac computers. If it's newer that whats listed here you're OK. Makes sure the SSD's firmware is also upto date. Did you enable TRIM services?
The next thing here is reformatting the disk as you replaced the SATA cable you should have done this. That way any errors on the drive doesn't mess you up. In addition, it would also verify the cable was good which still could be an issue. I add some tape around the folds to give the cable some additional protection. Also make sure the rubber grommets are present on all four mount points.
The last thing here is making sure the drive has free space. You should have 1/4 to 1/3 of the drive free (smaller drives need more space). Also clean out the old cache & logo files. Here's a good tool on the App Store to make this easy: Disk Doctor.
Let us know what you find.
Your SSD is only a SATA II (3.0 Gb/s) this systems HD port is SATA III (6.0 Gb/s), it should work. But you may want to speak with Kingston. We don't use these SSD's so I can't tell you anything about them.
At this point I think you need to go back to the basics here.
First I would stay at Yosemite with the updates so you can enable TRIM services natively within the OS. Don't install anything else for TRIM services. In any case your issue is not with TRIM.
Now to the focus on the real issue here:
I think you need to monitor the processes within Activity Monitor. With it running to the side on your desktop see if you can recreate the issue what you want to watch is the drives I/O does it stop in mid action?