Image Preivew and thumbnail size

1. Is there any way to make all images being previewed (with the space bar image view) to always be displayed to stretch vertically to fit the screen (regardless of initial dimensions) without just zooming?

2. Is there any way to make all thumbnail images have the same height (regardless of initial dimensional differences)?

3. Is there any way to zoom in different increments than 100 200 400 800 %?