How can I loop through the values of a drop down within a SuperTable?
You'll likely want to do something like this:

{% for fieldtype in blocktype.getFieldLayout.fields %}
    {% set field = fieldtype.field %}

    Handle: {{ field.handle }}

    {% if field.type == 'Dropdown' %}
        {% for option in field.settings.options %}
            Label: {{ option.label }}
            Value: {{ option.value }}
        {% endfor %}
    {% endif %}
{% endfor %}


Essentially, this loops through all the sub-fields in your Super Table field, and for each field, you can make any sort of conditional you like in order to handle each fields content.