That would depend on how the exploit is written. If it is macro that loads code based on the OS and has both macros for both MS word for mac and Open Office then it could be a possible injection vector. Just to tell you most of the time they just use some generic file they pull of the internet and won't have anything important in it.
I agree, Why would you even open it. On the other side of it, It really depends on the malware. There isnt much malware on the OSX side. Most malware is meant to run specific commands on Windows, so any attempt in OSX would automatically make it fail. If it was browser based, then it will still install the same add-on and do the same damage as a Windows machine
You are correct, doc files cannot simply be converted to text files just by changing the extension. Here is an example of a .docx file loaded in the Atom text editor and as you can see it cannot parse the file correctly.
The file in question is a .doc not a docx meaning this method won't work. A .doc file is a Binary File Format you want to look inside of it a hex editor would be the best option.