"Yeah everyone keeps taking about HY Behavioral and now I'm debating if its worth the time/money to get it?"
--I think you can survive without it. FA is good for behavioral/biostats, and if you've had these taught to you in school, you're fine either way.
How hard are the behavioral questions on step 1, I don't know?
--For the most part, with a little bit of studying, they're pretty straight-forward. I think what you'll hear is behavioral isn't something to spend lots of time studying, but you should definitely look. They're equally weighted points, so it's worth putting in a little effort. With HY or just FA + practice q's, you'll be totally fine on the real thing.
Are the "what should you do?" questions tough?
--Again, with a little studying, they're fairly straight-forward. On any test there's probably going to be a few that are tricky or you're not sure, and that's how I felt on mine.