hi. welcome to the community! well, my advice to you is look around the market. there are other brands besides nikon (though i'm using nikon) . canon, olympus, sony...etc you might wish to take a look at their range.
which is suitable would depend on what you would require the dSLR for. e.g. for myself shooting planes and fireworks, as an entry level i got the D60 and upgraded the lens. a D80 might be a bit of an overkill , but depending on your budget as it would be considered a mid-range pro camera. entry levels are normally D40 to D60 ranges. anything with D*** is pro grade. Of cos there are pros and cons about each and every camera. Just beware that it might not be up to your expectations. look around. no hurry!
1) Look at your interest level. If you're just taking up as a hobby or just getting a feel of it, get a D40 or D40x. But if you have a strong passion for Photography, i suggest you go for the higher end ones. Maybe even save up more cash for a DXXX
2) Think about what you want to shoot, EG. Sports you gotta have a higher FPS. Portrait, you'll do fine with almost any camera (more on the lens), etc...
3) Size/feel. You have to go down to the shop and feel the camera for itself. If you have huge hands, the D40 would be very very small!
Echoing the above too. If you're just getting into the hobby, don't have much disposable income, not sure if you're going to stick through this hobby long, then it makes sense to minimize your initial investment first. The D40/D60 are pretty OK starter cameras, though the D80 has more room for growth at a higher cost.
i'd say for general shooting, the Exposure Bracketing and DOF Preview are not critical functions.
Exposure Bracketing - camera automatically take a few exposures of the same scene. eg -2, -1, 0, +1, +2 stops. useful when u dun trust the meter of intend to do things like HDR.
DOF Preview - stops the lens down to the aperture set for exposure so that u can preview the DOF. u see, to facilitate focusing, composition, when u view through the viewfinder, u always view through the biggest aperture (no matter what aperture u set). the moment u press the shutter release, the aperture is stopped down for the shot. if DOF control is so critical to u, u can always view it from the LCD and then compensate accordingly.
i dun even know if my camera has these 2 functions, cus i dun use them.
Well, for those photo subjects you've listed below, any DSLR would do at least reasonably alright; the lens however is going to be the issue. If you're not going on sports shooting, a lens like the popular 18-55mm VR would suit you nicely as a starter for your D40/D60.
Once you get into the hobby and can spend a bit more, then you can consider one of the ultra-wide angle lenses, like the Sigma 10-20mm which is discussed on another thread now.