What element is totalsBlock? Since you are inserting table rows in it, totalsBlock should be <tbody> and not <table>.
Code:
<table>
<tbody id="totalsBlock">
</tbody>
</table>
And when you are looping through the fields to build the form data, you need also to escape the field name because you have special characters (e.g. update_totals[2][title]) in it.