The path variable in minion.xml is Base64 encoded, which is why it looks like random garbage. I'm not sure why it's encoded, there's no real reason that I could think of, since Base64 actually makes ASCII strings
longer. https://www.base64encode.org/ is a quick place to mess with that but it's probably correct anyway.
Be sure to use backslashes (\) instead of normal slashes (/) in your path, that seems to hang it. I guess that's because it's a Windows-style path, but I haven't seen an app that really cares which way the slash points in a while. I thought Java was immune to that anymore.
Extracting the .jar from the Windows EXE may not be a trivial task, since it's not readily accessible with archive unpackers and it doesn't appear to unpack itself into the temp directory. Extracting the Mac DMG's jar didn't work either, since as mentioned it just kind of hangs once it gets to the main screen.
Personally, I was only able to get Minion in WINE to see my WoW directory once, after which it went through a period of crashing, and now won't see any addons. Quite frustrating. Also, I had to use a 64-bit prefix, or it wouldn't run whatsoever.
Edit: Using Oracle's Java 1.7.0_55, Ubuntu 14.04 x64