Hi Sean,
Your above code load that font family, you need to apply that font to any element on your site, just like the p tag that you added. As you can see here, this font is working for p tag: http://prntscr.com/oodaqn
You need to apply for other elements like you did in Nebula custom css file, for example:
a {font-family: EuclidFlex-Regular !important; font-weight: 400 !important;
color: #e50000 !important; text-decoration: none !important;}
a:hover {color: #2e2c7c !important;}
h1, h2, h3, h4, h5, h6 {
color: #2e2c7c !important;
font-weight: 600;
text-shadow: 0px 0px 0 rgba(255, 255, 255, 0.15);
font-family: EuclidFlex-Regular !important; }
.icon-check:before {
font-family: fontawesome;
}