Option 3 looks the most likely for me.
1st step: Download ffmpeg for mac, from this site: https://www.ffmpeg.org/download.html
2nd step: After downloading, put the ffmpeg file, in a folder, then get the path, that is pointing to it.
3rd step: Open up replaymod, click on the render button.
4th step: Go to the "Command line settings tab"
5th step: There is a small, input box, on the left, saying "command". Just put the path of the ffmpeg file in here
And just render normally. It probably will work, but i'm not sure, because i'm not a Mac user.