Did you actually try different USB ports rather than go on your belief that there are no problems?
I don't know why you can't install JL__CMDER. That may be something with regard to your computer that you have to sort out yourself.
I've heard of people who have gotten support at a store with wiping and reinstalling an OS, and that might be an option for you.
But it sounds from your descritpion that you must wipe the device first, before you can install the OS.
I believe the desktop manager screen you are seeing is because desktop manager is looking for the device software (the OS) for your model on the computer and didn't find it.
I suspect you were running the device updates directly from desktop manager. There is another way: You download the device software yourself, run the installer, then use desktop manager or loader to install it on the device.
If you continue on your own and you are able to wipe the device, see the latest OS thread for your model at the top of the forum for instructions on installing the OS.
If you feel you are over your head, contact a store in your area and see if they can help you out.