Christina,
Please read my previous post again with my apologies. I added hopefully helpful information after you posted your response to it.
Now, back to your posts...
On the one hand, you mention that you like the first two photos the best for one reason and that you like the third image the best for a very different reason. Try to develop the confidence to be able pick the one single image that you like the best. Doing so helps you determine what is most important to you. Photography is almost always about making do with the compromises at hand, so it's important to know which compromise is the most acceptable. Waffling is not allowed.
About the criteria of a low-contrast image: I doubt that we could arrive at a clear-cut list of criteria that applies in all situations especially that all of us could agree upon. Even so, I'll explain why none of these images are low-contrast in my mind.
For me, there are two primary types of contrast -- the type that addresses the softness or hardness of a shadow and the type that addresses the difference in luminosity between adjacent tonalities. Regarding the first primary type, if the shadow is hard (well defined), that is a characteristic of a high-contrast scene. If the shadow is soft (not well defined), that is a characteristic of a low-contrast scene. Regarding the second primary type, if there is a strong, prevalent line in which the luminosity on the two sides of the line are very different (as in the case in all of your photos), that alone makes the photo at least a medium-contrast photo. If that difference in luminosity is great enough, it could be a high-contrast image even when there are no true white or black tones.
While you are correct that there are few true blacks or whites (if any) in these images, that fact alone is not the only criterion in my mind for a low contrast image. The authors of
Science: Light and Magic apparently agree with me, as the following is from page 23:
"The contrast of the light is only one of the influences on the contrast of a photograph. If you are an experienced photographer, you know that you can find high contrast in an image with low-contrast light and vice versa. Contrast is also determined by subject matter, composition, exposure and development."
I wonder if the first sentence in that quote explains part of the reason you and I at least for now see your images differently with regard to the amount of contrast. I wonder if you're thinking of the amount of contrast in the light, especially because you were at the scene, whereas I'm thinking of the amount of contrast in the photo. The two can be very different, especially if there is a strong prevalent line in the photo with contrasting tonalities on either side of the line.
Also, you mentioned that early morning light is soft, referring to soft blues, white tones and the lack of black tones. When photographers (correctly in my mind) describe the softness of light, they are not referring to the luminosity or the color of the light. Instead, they are referring primarily to the definition (hardness and softness) of the shadows. As an example, it's quite easy to make a photo using only pastel tones and hard light. Read the stuff in
Light: Science and Magic about all of that on pages 16 -23.
You mentioned that the fourth and fifth images aren't keepers. That being the case, I think it will help you in the future to explain that when posting images that aren't keepers and to also explain why you are posting them. Otherwise, don't post them. That's because, lacking an explanation, most people will probably think you believe they are keepers, which is ineffective communication leading to even more ineffective communication.
You also asked for tips about how to recognize that a particular three-dimensional scene will not work as a two-dimensional photo. To be fair, that's probably the single biggest problem all photographers have and certainly my biggest problem. Otherwise, we wouldn't choose to show others only 1% to 5% of our photos.
Even so, those of us who attend to the situation do get better at it over time. Maybe the best way is to first recognize that a particular photo doesn't work, as in the example of the two photos that you determined are not keepers. Then identify the characteristics that were compelling in the scene that aren't sufficiently compelling in the photo or are perhaps overridden by other characteristics of the photo. Then determine why that's so. Having done all of that, remember what you determined the next time you are at a scene that has similar characteristics.
All of that requires eliminating all of the emotion when we're at the scene and when we're remembering the scene while viewing the photos. That perhaps is my best recommendation: remove the emotion and be extremely critical in the most objective way we can possibly muster.
Lots of stuff to consider! (Discussing this stuff helps solidify my thinking about recognizing the qualities of light, which is what photography is all about.) Hope this helps!