I figured out how to fix it in the straight HTML, but I still don't have a solution that'll fix it as part of build website, so I'll go ahead and open a GitHub Issue. (If someone else has suggestions, I'm all ears!)
To fix the Empty Button error, I added an sr-only span.
Original:
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar">
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
Update that clears WAVE check:
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
To fix the Broken ARIA menu, I removed the button role and aria-expanded.
Original:
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">
Resources
<span class="caret"></span>
</a>
<ul class="dropdown-menu" role="menu">
<li>
<a href="resources.html">Crisis Resources</a>
</li>
<li>
<a href="reading-list.html">Reading List</a>
</li>
<li>
<a href="STEMM-orgs.html">STEMM Organizations</a>
</li>
</ul>
</li>
Update that clears WAVE check:
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">
Resources
<span class="caret"></span>
</a>
<ul class="dropdown-menu">
<li>
<a href="resources.html">Crisis Resources</a>
</li>
<li>
<a href="reading-list.html">Reading List</a>
</li>
<li>
<a href="STEMM-orgs.html">STEMM Organizations</a>
</li>
</ul>
</li>