We are unable to assign a Font style (“formlink”) or any styles to FindReplaceOptions object. Please find the below code snippet which throws Null reference exception. Looks like the options.ApplyFont only has Get property not Set property.
FindReplaceOptions options = new FindReplaceOptions();
options.ApplyFont.Bold = true;
// options.ApplyFont.Style.Font.Style = style;
options.ApplyFont.Style = style;