Accordion/Static Nav Fly-Outs Puzzle?

I’m working on a theme, here:

Trying to get my static-positioned fly-outs to push the main content down the page when they are open (while also remaining static), instead of overlaying on top of the page.

(Clicking the “Topics” button triggers the fly-out.)

Currently it is this:

The behavior I want is this:

There is a little bit of Javascript along with the CSS making this happen.

This is just a little bit over my head on how to make this behave how I want.

Any help would be very much appreciated!