Camera level
Camera tilted up
Same tilted up photo corrected in Photoshop
Temporary backdrop wasn’t quite big enough, shots were hand held without measuring so slightly off, but you get the idea. Sorry for the Perrier commercial, I wanted something that was square and this box was the first thing I came across. We know the box is made of rectangular shapes, and I didn’t touch it from shot to shot, so the adjacent sides should be parallel (within the limits of box making) In the top photo, the sides are parallel. In the middle photo, the top edge looks shorter than the bottom edge and the sides lean in. In the bottom photo the sides are reasonably parallel again because I adjusted the middle photo in Photoshop. Turns out the edges’ lengths vary by about 1/16th inch, who would have guessed! Sides of buildings should be parallel to each other and perpendicular to the ground, except a certain tower in Pisa. If all your buildings lean into the centre, there is lens distortion.
Usually the effect of pointing a short lens up or down is more pronounced than with a long lens. The same physics are at play as when you shoot a portrait with a short lens, which causes near objects to appear much larger relative to objects slightly further back in the frame, giving someone an extra large nose or other appendage if it is held nearer the camera. Portraits are usually shot with 85 to 135 mm lenses. This way you can stand a little further back and objects stay in perspective.
Bouncing children (and dancing adults) need more depth of field to keep them in focus, and higher shutter speeds or light from a strobe to freeze motion.
No comment on any of the others, means we didn’t comment on the others. Reasons vary from individual to individual but many of us when faced with a collection of photos pick the ones we want to comment on and leave the others for someone else to comment on.
I looked through your portraits and the shadows don’t look too bad. The one with harshest shadows is the restaurant and jukebox photo. For that sort of shot, bouncing off of the ceiling or a white reflector a few feet from the flash will soften the light quite a bit. If you can get the light up high, either bounced or on a stand, then move your subject away from the walls and their shadow will fall behind them instead of being well defined on the wall right behind them. If you can do off camera flash, sometimes a bare head off to the side will create harsh shadow that we call dramatic light. This can work well if you want to hide something, or you want to emphasize wrinkles.
I didn’t see EXIF data and don’t know what gear you have. Nikon and Westcott make stands with umbrellas and/or softboxes designed for small flash. If you need more power, you can even put two or three lights in one umbrella or softbox. This gives you equivalent power to most studio strobes but they take up a lot less space in a bag. The Nikon umbrellas come with their own bag. The Westcott stuff does not.