How to get Twenty Fourteen to show full width with breaking footer widget layout

My theme uses Twenty Fourteen as its parent, but the width on my pages seem to be limited on browser windows with a width > 1260px.

I have tried using this code…
.site,
.site-header {
max-width: 100%;
}
…which does fix the problem but introduces a new problem in that my four widgets areas in the footer are no longer in one row, but split (badly) into 2 rows – and setting the width of those widget areas does not fix the problem as it seems their absolute positions are dynamically generated.

So, how to get Twenty Fourteen to displays full width with breaking footer widgets layout??

Thanks!