Sounds like you are more than 90% of the way there. You need more understanding of geometry and spatial relationships than you need algebra.

As for algebra, the most complicated thing you need to understand is the inverse square law (don’t let the term intimidate you) that explains how light falls off the further a flash is moved from the subject. Get a grasp of that (and flash guide numbers) and everything else will be straightforward. If the first text does not make it clear, try another one.

The remaining relationships are easier.

This comment comes closer to explaining why the shot looks odd, other than having used a wide angle lens for a "portrait" shot. The problem is not the geometry of the picture, some of which can be fixed with leveling or cropping.

The issue with the lighting is the color temperature of the flash (daylight) compared to the sunset. They are so different that they do not seem to belong together. Also, having the sun right behind her head emphasizes the difference.

I know that some of you may not like some of Ken Rockwell's views on equipment, but he makes many valid points in his November 2012 article: http://www.kenrockwell.com/tech/why-we-love-film.htm

It's a long article worth reading - he seems to have checked all of the boxes.

Your priorities are different from mine. I do my own B&W processing for 35mm, 120 and 4x5 and then scan it myself. I can afford to have my color developed in a lab because I don't need to update my digital equiment very often.

When I need to take hundreds of snapshots I used my D70 or a D7000 and for convenience I can use my smart phone or Coolpix.

It's good to have a choice.

Not quite correct. Kodachrome was first and Agfacolor followed but this was before WW II. During WW II, Agfa and Kodak continued development imdependently, Kodak did not get its technology from Agfa.

I have not found Kodachrome to be more fragile than Ektachrome or other film. To the degree that you can trust Wikipedia:

Limitations of Digital ICE

Digital ICE is used to detect scratches and dust during transparent film scan and is not applicable for opaque document scanning. Where Chromogenic black-and-white films are supported by Digital ICE, other black-and-white films containing metallic silver (which form from silver halides during the development process of the film) are not. This is because the long wave infrared light passes through the slide but not through dust particles. The silver particles reflect the infrared light in a similar manner to dust particles, thus respond equally in visible light and infrared light. A similar phenomenon also prevents Kodak Kodachrome slides from being scanned with Digital ICE (Kodachrome's cyan layer absorbs infrared).

Although special handling of infrared may reduce the problem with Kodachrome, it is not likely to eliminate it.

There is probably no alternative to cleaning the slide as carefully as you can and then spotting to fix the dust spots that could not be removed manually.

Film and digital both have their place and many of us do both. Neither is "better", despite the strident arguments of some zealous fanatics.

For most of us, photography is a hobby and it should be fun. It's not about the cost or the resolution or the "accuracy" of the medium. If you get more pleasure from shooting film, don't be dissuaded.

Nikon would not risk their reputation by applying different design or quality control standards to China, Thailand or any othe country where their products are made.

The main reason for Nikon to produce equipment outside of Japan is economic. Another reason would be to lessen the exposure to a natural disaster, but that did not work out too well recently.

It is very likely that if you are driving a Japanese car, it was actually made in the North America , as are many premium European brands.

Unfortunately, Digital ICE will not work for Kodachrome or B&W.

Film cleaning solutions are not much help either since they are likely to damage the film surface. Canned "air" can also damage the surface if held too close as it may contain harmful chemicals.

The only solution I have found after scanning over 25,000 slides and negatives is to brush off the dust with a camel’s hair brush. As a last resort you can try washing and re-mounting the slide.

It pretty much boils down to the effort and intent of the photographer rather than the result. If you just fire off a shot, it's probably a snapshot. If you take the time to compose, focus and frame the shot, it is more likely to be a photograph.

But there are lots of snapshots that are better than other photographs. This could be just due to luck or the natural skill of the photographer taking the snapshot or the lack of vision of skill of the one trying to take the photograph.

It means that the center point will [try to] line up both horizontal and vertical lines in its equivalent of a split image focus, upper and lower points will line up vertical lines and the remaining points on the central row will line up horizontal lines.

Most AF is not very reliable for lenses with a maximum aperture smaller than F/5.6 (too dark). Apparently the camera you refer to may not be as sensitive in the center to vertical lines as it is to horizontal lines.

Look for a manual SLR with a focus screen with a split image focusing aid in the center to get a feel for what the AF is trying to accomplish. You will also see why it is difficult to use the split image if the lens is stopped down below F/5.6.

A new V750 is priced about $150 more than a V700 so you should check the specs to see if it is worth the extra bucks. Either will do a great job on 4x5 and you will have a choice of resolution (and resulting file size). They will even handle 8x10.

The carriers are delicate but I have not broken one yet.

You and I probably cannot afford a drum scanner. The Espon 500/700/750 scanners are reasonably priced and get a clear image of the film grain. And they handle a wide range of fim densities.

Try the Rollei/Agfa Pan 25. A little pricey but at least it is still around.

I use an Epson V750, which is only a little better than the 700 or 500 version. Also a Nikon LS9000 that is a little better but not worth the extra cost, even if you could find one used. All of these produce excellent scans.

For landscape, without breaking the bank, you might consider a Mamiya C330 with a couple of lenses from KEH.