"Every last detail needs to be crisp!"

You could also consider using a vibration reducing lens, a monopod (I have one of a walking stick variety), and a prime lens (single, fixed focal length) which has a greater range of apertures and fewer optical interfaces that distort and reduce the light.
The red and cyan artefact towards the edges is due to chromatic aberration, i.e. light of different wavelengths gets refracted by different amounts through the lens (the prism effect of Newton - a lens can be considered as a number of prisms joined back to back). There is a filter in Photoshop which is preset with the characteristics of a number of commercial lenses and this can be used to compensate for the aberration.
You can also try using only manual focus and exposure setting, and installing a split prism focussing screen in your viewfinder.

It's important to perform the lens correction on the raw image (best) or (if RAW is not available) at least before you have applied any other corrections (e.g. for colour balance, exposure, sharpness). This is because the filter set in Photoshop is keyed to the individual characteristics of the lens and camera and if you move the colours around, then the filters are not operating at the peaks they should be so the effect is lessened.

I'd use the basic tone controls in Lightroom 4 rather than fill light and recovery. Fill light can create halo effects around high contrast borders which your brain can interpret as over-enhanced image processing for sharpness.

I'm not sure what you mean by "is sharp contrast natural in cameras".

[EDIT - ADDITIONAL]
I've searched for a depth-of-field table for that lens of yours and I can't seem to find one.

I don't know if you've ever heard of the hyper-focal distance technique... but basically it runs as follows.

Your lens/camera combination will have a depth of field, i.e. a 3D block of space where objects that the lens focuses will appear to the eye to be in focus. The size of this region is dependent on a lot of things, but the main thing that you have control over is aperture; the higher the f number i.e. the smaller the aperture, the deeper the region is.

Now, this block of space occupies a region both in front of and behind the focal distance. If the focal distance you have set is infinity, then there's a region beyond infinity which would be in focus if it could exist. Such a region cannot exist, obviously, so you can focus on a point closer than infinity but within your DoF block and objects between that point and infinity will still appear to be in focus. This shifts the block of focussed space towards you, bringing more objects in the foreground into focus.

If you extend the principle to a tube station, then objects beyond the end of the platform cannot be seen (kind of), so you if you set the furthest region of your depth of field to that distance or slightly beyond it to allow for errors in reading aperture etc, you bring more of the foreground into focus. You see why I said about using manual focussing before... by the way, I'm a great fan of using film and non-auto-focus cameras!

[EDIT - MORE INFORMATION]

If you look here:
www.dofmaster.com/dofjs.html
you can work out a hyperfocal distance!
So for your London Bridge picture, given that the head or tail wall could be at most 115m away, you could set your focus manually to 3.3m and be sure (at f5 18mm) to get everything between 1.7m and 108m to be in focus, i.e. almost everything on the platform (as I expect you are around 1.5m tall and the camera's field of view would not extend to include your feet!)

Ah! I see. Well, the dynamic range of a camera is still woeful compared to our eye, which is logarithmic in nature. In those circumstances, I would use an auto-bracketed exposure sequence, layer the images in Photoshop and use the layer blending to allow the shadows and highlights to come through from the appropriately exposed image.

It almost looks like a painting...

Monopod.

Like I say, I have one built into my walking stick. :-)

EDIT

Just checked conditions of carriage and it now says that you can't use a tripod or other camera support system, so a monopod is out. :-(

But there is that body worn mounting system... who makes it??? Eboboo I think they are called.