Help with a HD reformat and Mountain Lion reinstall due to unknown type of hack, Malware, etc
This sort of infection is extremely rare in the OS X world. Getting reinfected over and over again is  even less likely. Not saying it's impossible, but very unlikely. 

I would start by installing Little Snitch and setting it to monitor outgoing connections. Also monitor your launchd folders using http://www.circl.lu/pub/tr-08/

The first step I would recommend is changing all of your passwords and using something like 1password so your ex can't get into something again. 

Marking this as a wiki so others can add suggestions since this isn't an "answer" per se. 

[2013-04-14: There's also Radio Silence which is an outbound filter like Little Snitch but supposedly simpler and less "chatty".]