[DNSB]

Further looking at your code;

<p id="e1016">16. <em>The Bewitched Continuum</em>, pg. 223<a href="#ref1016" "title=return to Chapter 10">&olarr;</a></p><br>
<p id="e1017">17. &ldquo;Mrs. Stephens, Where Are You?&rdquo; (#160)<a href="#ref1017" "title=return to Chapter 10">&olarr;</a></p><br>
<p id="e1018">18. &ldquo;Samantha on Thin Ice&rdquo; (#246)<a href="#ref1018" "title=return to Chapter 10">&olarr;</a></p><br>

1. epub3 requires every tag be terminated. So use <br /> instead of <br>.
2. You've quoted the entire title element. Use title=" instead of "title=
3. And again, replace the named HTML entities with their numeric equivalent.

See sample below.

<p id="e1016">16. <em>The Bewitched Continuum</em>, pg. 223<a href="#ref1016" title="return to Chapter 10">&#x21ba;</a></p><br />
<p id="e1017">17. &#x201c;Mrs. Stephens, Where Are You?&#x201d; (#160)<a href="#ref1017" title="return to Chapter 10">&#x21ba;</a></p><br />
<p id="e1018">18. &#x201c;Samantha on Thin Ice&#x201d; (#246)<a href="#ref1018" title="return to Chapter 10">&#x21ba;</a></p><br />

Best I can do for now.