looks like your html structure is wrong right now for the dropdown mechanism, which would explain why you can't style it properly.
Take a look at dropdown menu tutorials, like
this one, specifically the way they nest <ul>s and how the CSS interacts with each element.
of course most of them are horizontal dropdowns but it's the same principle with a few tweaks with regards to the positioning styles. there are tutorials which lay it out like the way you want but i didn't find a good one in my brief googling. anyways you should be able to figure it out pretty easily.