I'm thinking of majoring in JHU's Applied Mathematics and Statistics
(AMS).  However, I need more information regarding the career outlook
of AMS.

As I know, AMS is divided into 3 general fields: 
Probability/Statistics, Operation Research, and Discrete Math.

What kind of jobs are avaiable for these fields?
What's their future outlook?
What kind of certification exams will I have to take?  If yes, do they
limit the number of people given the certificate each year to a
certain number?

I know for Actuaries, there's certificate exams, but I couldn't find
more details .  Are there any certifications for Operation Research or
Management Science?

Also, as an AMS undergrad, what kind of Grad School is possible or
recommended?  What Grad majors are related to Operation Research or
Management Science?

Assume I decided on OR/MS as my future career.  What's a recommended
"path" to advance from undergrad to grad school, and what certificate
should I poccess?