If anybody is interested in running YOLOv2 Darkflow on nano here are some links that might help.
Video of Yolov2 Darkflow running on nano at 4fps: https://youtu.be/usdKZIZWSaE
Git hub repo with the instructions how to do it : https://github.com/valdivj/jetson-nano-yolov2-darkflow
I am currently migrating the deepstream reference app from https://github.com/NVIDIA-AI-IOT/deepstream_reference_apps/tree/master/yolo (trt-yolo) to python. currently it is pure cpp. It performs about twice better then the one you use. Will take me some time to do it as the code was not really designed for wrapping, but not too bad.