#1: You should use the same version -- right now: 188.8.131.52 -- both on your Mac as well as on the data collection machines. The version number (184.108.40.206) is identical for both Mac and Windows (cf. https://www.millisecond.com/download/).
#2: Inquisit data files are merely tab-delimited plain text files (you can simply take a given *.iqdat file, change the extension to *.txt and view it in any text editor). I have attached an example file you can use to try that out and see for yourself.
I'm not sure what happened with or to that GNAT *.iqdat file you attached. It certainly does not look like a typical Inquisit data file and appears to essentially contain binary data. Did you at some point during the data collection period set /encrypt=true in the GNAT script's <data> element and remove the /encrypt attribute at a later point?
FWIW, I have never seen anything like this happen to a data file and frankly have no idea (save for the /encrypt hypothesis mentioned above) what could have caused this. If you have any additional relevant information, please share!
In any case, to have the script record data (again), it should be sufficient to remove or rename the existing "2H. pGNAT.iqdat" in the script's folder to get a fresh file. Alternatively, you can have any script output separate data files per participant via the <data> element's /separatefiles attribute.
#3: It is unfortunately very hard (if not impossible) to diagnose the video freezing issue without access to the actual video files. (a) Could you please confirm that your data collection machines' Inquisit installations are up to date (i.e. at version 220.127.116.11), and if they are not, please update them? (b) Could you please provide the technical log file accessible via Tools -> View Log File... from one of the machines affected?