How to remove DaveGrohl10.7 spyware?

I would start by putting that file in the trash.
Then check start up items for anything unfamiliar and remove those.
Then reboot.
Then install little snitch.

Then you can see if anything else is asking for permission to use the network that you dont recognise.

If that doesn't work, you are into a world of hurt, a fresh install, recover data only, re-install apps one at a time.

p.s. from what I can see its not spyware, its a password recovery program.
So its possible it was used to access your passwords.

If I'm right, you need to change all your passwords online, which it pretty much seems you should be doing anyway because of Heartbleed. If someone is snooping on you, email would be the obvious first thing to change, followed by any financial accounts, eg bank, credit cards etc.

Honestly the best way is to backup your files (being careful) then boot up and use the disk utility to wipe the drive and do a fresh install.

If your ex managed to fall short on basic malware avoidance you don't know what else is on there and a compromised keychain is the worst thing you could be looking at.

And to emphasise again, all the OPs passwords could be compromised, so key ones need to be changed ASAP.

Not spyware

DaveGrohl is not spyware but a password cracker. Your ex was probably trying to get a login password. See davegrohl.org