@ThomasJacobs: Yes, then your Bluetooth is really incompatible (because such behavior was observed even before trying the ExtraMagic). You can try some other external Bluetooth adapter, there will be no conlfict (also usually it's possible to completely disable built-in Bluetooth from BIOS settings, or even simpler, from Device Manager, in your case by right-clicking "Intel(R) Wireless Bluetooth(R)4.0" and choosing to disable the device from context menu). So yes, you can try other Bluetooth solution.
As you can see from this thread, even outside the Boot Camp some people are very happy with ExtraMagic. But it's true, I always emphasize that a modern Mac running Windows is the target the ExtraMagic driver component is being officially developed for. Sorry for repeating, but to make it clear again, this doesn't mean the PC users shouldn't try the ExtraMagic. I would recommend to try, unless the target PC is controlling the launch of the space mission, etc.
To summarize, the best steps could be:
1. Just in case disable built-in Bluetooth as I suggested in the previous paragraph;
2. Pair the Magic Trackpad with your new USB Bluetooth 4.0 dongle, preferably featuring Broadcom chipset;
3. Make sure the Boot Camp drivers are active (e.g. trackpad should be able to scroll with two fingers);
4. Run the ExtraMagic installer Step 2;
5. If after reboot the ExtraMagic Settings app says it couldn't connect to the driver, re-run the Step 2 one or two times.
About uninstall: you can uninstall normally, via Programs and Features. If the driver component failed to install, there will be no "Apple Wireless Trackpad (ExtraMagic)" entry in Windows Device Manager --> Mice And Other Pointing Devices. But if there exists such entry, you can right-click it and choose to "Update..." --> "Search Automatically..." and the stock driver shall be back.