Hello,
the drop-down in a matrix is not a buildt-in feature, but an javascript workaround.
So it is advisable you show us this script.

And your second question:
Whhich text?
subquestion text? answer option text?

If you will do this just once, write your css-styling into the text, like
<span style=font-size:18pt">Subquestion 1"</span>
<span style=font-size:16pt;color:red;....">Option 1"</span>


But if you would like to have this for all your surveys you should add it to the custom.css of your theme.

Joffm