You will not be able to run Dell Recovery from an SD card, only USB or mass media devices. I've had the same problem with my DV8P the other day, I installed W10TP and couldn't roll back because it overwrote the recovery partition with its own. Downloading factory image also didn't help as in order for recovery to initiate, you need to have power AC attached as well as the media which means connecting two USB with one port. You need to have the USB power/data splitter to do this.
There is also another method(which I used in the end) - boot any OS from USB/SD/LAN/whatever, then manually recreate everything (not just recovery partition but also system, data, and the fourth one) using diskpart command in CMD. It took me a while typing everything in but I succeeded in restoring the partitions, then I simply pushed the factory Dell image which I downloaded earlier onto the system partition.