Adding logo causing site content to shift down

Hi! The theme is fun to work with so far. Thank you!

I’d like to modify how the logo is displayed in my header in one of two ways:

1) Add padding to the top and bottom. I tried adding 15px padding to top and bottom in the #site-navigation .container CSS class. I also tried adding padding to .site-branding-logo in the CSS. These work to add the white space I’d like; *however*, it causes the entire site to shift downward just before it finishes loading, so I removed the custom changes. Any suggestions?

2) Can the navigation background be made transparent? What is the CSS for that?

Thank you so much for your help!

The page I need help with: [log in to see the link]