It might be of interest to see how a three-step-darktable-solution handles the image.
- Step 1: in lighttable, merge the three images into an hdr-dng.
- Step 2: in darkroom invoke the Initial Workflow lua script, written by @Ulrich_Gesing.
- Step 3: export result:
And between steps 2 and 3, feel free to tweak whatever you like.
More script info here: Working with modules from Lua scripts in darktable - #42 by Ulrich_Gesing
Have fun!
Claes in Lund, Sweden