Getting nervous!!! I applied as a senior undergrad, didn't get it. Now reapplying this cycle as a grad student for my 2nd and final attempt! Ugh please just end it already.
It's best if you keep them separate and explicitly have bold headings saying "broader impacts" and "intellectual merits". Reviewers will score you on a scale based on those categories so you have to make it easy for them to distinguish between the two. Also when you download the template it specifically says to include those headings. Good luck!
Seems like not a lot of people are talking on this thread. Has interest for applying this year waned? I'm making some finishing touches before I submit in a few days.