I figured it all out, along with some help in another thread. Thank you so much (everyone!)
For those looking to alter the fonts across the board, here are all of the relevant entries I found (that mattered to me). I put these in custom.css (I'm using yootheme/warp7; for others it might be template.css); You can adjust the numbers to your preference.
body div#fd.es .es-stream-meta .es-stream-title {font-size: 20px;}
body div#fd.es .es-stream-meta .es-stream-title a {font-size:20px;}
body div#fd.es .es-streams h4 > a {font-size:20px;}
body div#fd.es .es-stream-content {font-size:15px;}
body div#fd.es {font-size:20px; }
body div#fd.es .es-dashboard .es-container .es-sidebar .fd-nav-stacked a {font-size:15px;}
body div#fd .fd-small {font-size:15px; font-weight:normal;}
body div#fd.es .es-toolbar .toolbar-user-name {font-size:15px;}
body div#fd.es .es-comments-form .es-form .mentions textarea { font-size:15px; font-weight:bold;}
body div#fd.es .es-stream-meta .es-stream-meta-footer {font-size:12px;}
body div#fd.es .es-story.is-collapsed .es-story-textfield {font-size:20px; font-weight:bold; line-height:16px; top:16px;}
input, button, select, textarea { font-size:20px; font-weight:bold;}
label, input, button, select, textarea {font-size:20px; font-weight:bold; line-height:20px;}
body div#fd.es .es-story-textfield {font-size:15px;}
body div#fd.es .es-widget .widget-title {font-size:13px;}
body div#fd.es .es-widget .fd-nav > li > a {font-size:15px;}
body div#fd.es.view-conversations .es-content li.conversation-item .conversation-meta {font-size:15px;}
body div#fd.es .es-notifications .es-item-list > li .es-notification .es-time {font-size:15px;}