Displaying image size in PS

Zoom tool questions:

When I use the Zoom tool's Fit on Screen option, sometimes an image will
display in a window with a gray border around it, and sometimes without
the gray border. What is causing the difference, and how can it be
controlled?

When alternate between the Zoom tool's Zoom In and Zoom Out options, the
window size changes. After zooming in for a small window size, zooming
out will change the window size with the vertical dimension maximized.
Is there a way to zoom out and keep the smaller window size?

After two images are set up to display in two windows side by side,
these two problems are very annoying when zooming in and out.

Ruler question:

When displaying an image with View Ruler turned on, an inch on the
screen is smaller than an actual inch. Is there a way to make the image
inch the same size as an actual inch?

Thanks.