First let me say these are not bad at all, any of them.
However, and this may be a 'terminology thing', I am confused by some of your statements, as may some others, who then may give inappropriate advice - so I think it is helpful to explore the use of the correct terminology.
To me "exposure" is the combination of all the three sides of the exposure triangle;
Aperture (primarily to control Depth of Field - DoF)This should result in an image that is 'just right' in terms of brightness, not things like how blurred movement is or how sharp distant things are.
Shutter Speed (primarily to control motion portrayal)
ISO (primarily just a means to get the values we want for the other two)
As shown here, the exposures all look pretty good to me, they're not too dim, or exhibiting unduly blown highlights, so I would not change the "exposures" - although we might usefully tweak some individual elements of it.
Of #1, you say;
If you shot #1 at f/16 at 31mm on a DX camera (Nikon D40), I agree (without looking it up on a DoF calculator) - I would expect the second stall to be sharper - although it is called "Soft Pretzels"
This image doesn't have the crispness of the other two and is generally noisier. I believe that some of this has to do with the longer shutter speed but I am wondering if f16 was a bad decision? I expected the background building to be sharper with that exposure while still capturing the movement in the lights of the Ferris wheel?
This makes me wonder if you made the best use of the available DoF at f/16 and begs the question; what did you focus on?
If I had tried shooting this, I would focus on say the word "Popcorn" or "Candied" towards the back end of the first building. If you focused in the obvious place, the centre of the image as we see it now, that would be the closest part of the structure and would 'waste' a lot of your DoF on the empty space in front of the stall. If you need more detail on this, just ask; "why?".
Of #2, you say:
I think you really mean a shorter shutter speed, achieved through use of a higher iso, giving the same exposure, but the effect you wanted; a sharper image because people would have moved less if the shutter speed had been faster than 1/8s.
This met the goal of capturing everything with minimal movement but I wonder if a different exposure
would have worked better (this is the shortest shutter speed of the three)?
F8 1/8sec ISO 100
Of #3, you say;
The bits that are liable to be moving are quite a bit further away in this one and that helps, plus it may have been chance; ferris wheels and roundabouts/carousels stop to let people on and off, is it possible this helped?
This one is the crispest (although downsizing did add a fair bit of noise) with the nicest light despite having a longer shutter speed than the others? I'm confused
F8 .8sec ISO 100
You shot them all at iso100, so none of them should be particularly 'noisy' - unless you are adjusted brightness/exposure upwards during in PP, and/or cropped any significantly.
Finally, downsizing (alone) can only reduce noise, not increase it, so if you think it is increasing noise, either what you are seeing isn't what I'd describe as noise, or there is something else going on when you "downsize" (perhaps some automatic sharpening?)
Shane, you definitely have an instinct for an artistic shot and you know roughly what to do, you're perhaps a bit fuzzy on the technicalities at the moment, but we can help with that. I just hope I haven't been too pedantic and put you off, that's the last thing I want to do.
Overall, I would appreciate any and all feedback but would be especially appreciative for any focused on the subject of the exposure triangle and shooting at night. If I am not identifying the correct problem then please enlighten me...
Hope that helps,