Just wanted to drop this here in case anyone else is looking for the answer, as my SP was able to help me with this.  We ended up targeting the specific field which we determined by assigning the form to a user task, set as read-only in the task assignment and then inspecting the element using the developer tools.  The CSS below worked to target the text box, increase the font size, make the background white (making it much easier to read), setting a border, and making the height auto-adjust to match what is needed based on the amount of text in the box.

/* For "Other" description box in saved mode using specific ID */
div#Field111_other_value {
    font-size: 30px !important;
    line-height: 1.5 !important;
    width: 100% !important;
    height: auto !important;
    padding: 10px !important;
    background-color: #f9f9f9 !important; /* Optional */
    border: 2px solid #ddd !important; /* Optional */
}