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Just putting my resolution here in case it is helpful to anyone else googling this issue. I just found and tried this by googling / reading... I used the BoldGrid backup before changing anything (since I really don't know a thing about coding CSS).

In the Customize, I went into the Custom CSS/html text editor. Found this part

/* Inside Pages */
.site-content {
margin-top: 10px;
padding-bottom: 25px;

The 10 and 25 were much bigger numbers before. I just adjusted, saved and refreshed the preview in another tab until I got the look I wanted on both a desktop and phone.