When done using orbit SketchUp doesn’t help you get the eye height back by itself. That’s why I do this kind of navigation completely manually with look around, orbit, pan and mouse wheel as opposed to the walk around tool. I agree that arrow keys (or WASD) would be much more intuitive for first person view.
Regarding the units you can go top Windows > Model Info > Units and change them to meters or centimeters.
To get the camera to a defined height over the floor, activate look around tool, type the length and press enter.
Happy birthday btw! (the forum displays a cake next to your name)