from your directory names and slashes, i suspect you're running a linux
that's the cause of your first issue, 32bits or 64bits. executables of the wrong bits give that message
i've just checked my download Arduino_STM32-011016-1730.zip, both sets of dfu files are the same size
and all are 64bit format.
it's back again, both linux and linux64 are compiled for 64bit
i had this problem about this time last year. it was most frustrating
seems it's supplied from a 64bit system; it was suggested a virtualbox 32bit linux install could be used to produce them.
if you are 32bit, it's an easy enough recompile, you'll need the relevant support files.
if you contemplate moving to 64bit its not that difficult, one essential is having a separate home partition.
you will also need the files to allow 32bit executables.
debian jessie 8.x 64bit is definitely recommended
messages about include files usually mean you'll need to install the dev files.
for this one under Debian at least; are these
one of them may well be there from installing something else