Hello,
Please add the following to the bottom of your template.css file and this should fix the buttons
.bigbutton {
display: inline-block;}
The menu is dropping because your logo is too wide and has a lot of white spacing to the right of the actual logo. You need to crop off the white space on the right of it and adjust the width here (perhaps change to 300px or so):
#s5_logo
template.css line 492
As for the text not centered open the s5_responsive.css file and remove the margin-lefts located at the following lines of code:
250, 262, 314