Re: USB 2.0 actual transfer speeds
You're confusing your MBs and Mbs.
USB 2.0 is 480 Mb/sec. Megabits. That translates out to about 60MB/sec for the entire chain (if you use more than one USB device, you cut that amount down accordingly, and since you're saying two USB 2.0 devices, that's not unrealistic to expect that kind of cut that you're experiencing)
USB cables also, for the most part, don't care about the USB spec. I've used old printer cords from 5 years ago with USB 3.0 ports and it still worked at USB 3.0 speeds. They just changed the signaling of the standard, not so much the physical aspect, which is why you can use USB 3.0 on USB 2.0 and 1.1 ports.
8.5MB/sec is actually average for what you are doing, and depending on what you're transferring, the speed can rise and fall accordingly. When it does lots of little files, it can show a "slow" speed like 8.5MB/sec, and when it's doing large files, that number may go up as it has time to estimate the true speed.
I wouldn't read too much into it.