Add the following style to your template, and it should fix the button:
.fb_button { line-height: 100%; }
As for transparent background for the Fan module, unfortunately, that's not possible. Facebook only lets so much customization to be done to their module, and that's not an option. Facebook is picky to make sure that their widgets are consistent across sites for the same user experience and branding, and that means less flexibility in customization is possible.
Sorry we can't help with your second issue,
Alex
Login button apperance
