Mobile Menu Invisible

http://www.historyofphilosophyofscience.org/ When my site jumped to the mboile menu, two strange things happen. 1.) By opening the mobile menu, it expands to the primary nav, but the options are too far on the left to be seen. How do I shift it to the center and make sure it isn't covering any content? 2.) When you open the mobile menu, the "MENU" text stays in the middle and can't be closed. How do I change the z-index to make it clickable and move it out of the way of the opened mobile menu?