Cross-Browser Problems and Static Menu/Text

I’m new to PHP and CSS, so bear with me as I try to figure out all the little details.

First, I’m having issues with cross-browser compatibility for my blog at https://www.vu.union.edu/~majora/wordpress/. On Firefox in particular, the two columns on the right are often pushed down to below the content area. I’ve tried adjusting the width of the content area and the two sidebars, but I’m still having issues. Is there a way to force the two columns to the right of the content area, possibly by making them variable while maintaining a static overall body width?

Second, I would like the text and the menu at the very top of my blog to line up with the header photo. I’ve tried padding, but it’s too variable between browsers. How would you ensure that those two elements always line up with the header photo beneath them? Thank you very much for your help.