I'm not sure why the trolls are so interested in you, that 'I'm in love' guy seems to have developed an unhealthy obsession for you, but why?
No you can't find out the IP address of Y!A users, or where they're from. Yahoo keeps that info secret, and for good reason. If that info falls into the wrong hands, some serious trolling could be done.
Yahoo!7 is the australian site, au.answers.yahoo.com
Yahoo!Xtra is the NZ site, nz.answers.yahoo.com
Yahoo! is the normal (or USA) site, answers.yahoo.com
Just because someone is using the Yaho!7 doesn't necessarily mean they're from Australia though, someone from somewhere else could easily get into the Australian site just by changing 'nz' to 'au', for example, in the address bar. Or by clicking the Aussie flag at the bottom of the screen. If the email comes up 'Yahoo!7' it just means they were using the Aus site at the time they sent the message.
I've frequently found myself ending up on the Australian site just byclicking the link to another question in an answer to a Y!A question, that was posted on here. So it's really easy to go from one country's site to another.