Note that the first JPEG image is blurry and second is strongly overexposed. Only the last one contains a useful image.
There could be many reasons why it was impossible to recover the response curve. It could be because there were too few JPEG images, the image quality was not sufficient, or the camera alters response curve every exposure and thus breaks the assumptions of the algorithm.
It could be possible to recover a camera response curve on one sequence of exposures (possibly more than 3 images) and reuse it on other sequences.
I would recommend to either capture RAW images or more JPEG exposures. For this particular sequence, I would suggest to fake HDR with:
pfsin SAM_5545.JPG | pfsgamma.exe -i 2.2 | pfsclamp.exe --min 0.001 | pfsout trees.hdr
2. Indeed the optimization gets stuck on this image and does not converge. I did not have time to investigate it. But I got useful images with:
pfsin SAM_5545.JPG | pfssize.exe -r 0.25 | pfsgamma.exe -i 2.2 | pfsclamp.exe --min 0.001 | pfstmo_mantiuk06.exe -v -e 0.5 | pfsout trees_ce.exr