OP – glad you seem to have got it sorted out. As hard as it seems it does get better. I'm fortunate that my missus didn't get the whole emotional rollercoaster thing for our first and seems to be the same for the second (22 weeks in), but as the realisation dawns that your life is about to change forever it can get very very scary.
The best advice I can give is that you both sit down regularly and talk about how you're feeling, sounds a bit airy fairy I know but it really does help you get through it. Most of the time it's probably some underlying fear that's making her snap, like how painful the birth will be, what the hell you do when you get home, etc etc that is triggered by your bad cooking. You must have a lot of worries too (I know I did), so by telling each other what they are you can help to alleviate each others worries and understand a little more about why you both behave the way do.
+1 for the ignoring all the websites, books etc (or at least taking them with a pinch of salt), find your own way. You'll be sick of every man and his dog offering advice soon enough (us here included!).
As for once the baby arrives, that's hard too! But wonderful also. The first few months for us was very hard as he was colicky (sp?) and wouldn't stop crying, if you need help don't be afraid or ashamed to ask for it. Friends/relatives with kids will all understand and be more than happy to help out here and there – take them up on it and go out for a meal and a film or something.
There will be times when you'll wonder what the hell you've done, but once he/she hits 3-4 months it'll all drop into place and will feel like they were always there. It'll still be tough but you'll start to see what it's all about.
Good luck!