BigJim,
Man oh man. I'm so sorry. Just keep in mind that most JW are not thinking for themselves. Someone else is doing it for them. So when she says those things, she is reacting out of what the WTS has taught her not what she has thought on her own. Be patient with her...I know...easier said than done.
Spousal smoking isn't grounds for a scriptural separation. But Blondie is right - that doesn't mean the elders will give her good Biblical counsel. They may even try to conjur up lies as they have in other situations we've heard about. Don't underestimate their determination!
Perhaps instead of being frustrated that you do the things she hates, she's actually feeling neglected? Maybe you could lay low for awhile on the smoking and pamper her/romance her/seduce her, she'll remember why she fell in love with you in the first place. I think taking her to karaoke so she sees it's really okay is a good idea. Maybe she just needs a little womanly (not necessarily sexual) attention. I just get the feeling that the smoking issue is just the tip of the iceberg. There is something deeper bothering her and she either doesn't know what it is or is not willing to share at this point.
There have been times in my relationship that I've felt very insecure and unhappy. The best thing that my boyfriend did was to just talk calmly and listen to me. He didn't always understand where I came from, but at least listening to what I had to say (without interrupting and trying to argue or fix it) did me worlds of good! It really made me think, "You know he's not perfect, but look at all his great qualities!" Maybe you could just sit down and listen to her heart?
But I highly recommend not threatening her with exposing "The Truth" to the kids. Threats come across as Devil's work. It'll just scare her off even quicker!
Just a few thoughts...
Billygoat