In what order are supposed to install the files? Which do you launch first?

I mean, there are countless files in the offline download and quite frankly, it's absurd!

Oh and please don't mention the Galaxy install because that failed...
(Presumably due to my previously having used Steam)

How much space do you have free? I really would work out your galaxy issue because if that's failing it's likely going to fail with the offline installer too.

1st Delete the 4 files that start with "patch_" you don't need them.
Now run "setup_pathfinder_kingmaker_2.1.7b.fix._(47677).exe"

The .exe files that remain after this should be the DLC which can be installed in any order.