Setting strip height to viewport size

https://www.wixproisrael.com/demo1

This solution is great. I am having two issues with it though: (1) how to subtract the height of the nav bar? and (2) if there are any other elements in the strip, they get pushed up or down from the text in the code. Is there any way to either subtract the height of these elements or preventing them from vertically aligning with one another? Thanks