HI Warren,
With regards part 1, “will getting a PMP help my career”, you can answer this yourself. Go on some job boards and search for the kind of jobs you are looking for, if you see PMP coming up as mandatory or desirable, part of the questions is answered. In regulated industries, in many cases you can’t get through the door for an interview without a PMP, in other industries its less of a requirement. But I recommend do some job searches and see how often PMP comes up as a required certification.
But even with a PMP experience still matters, a good job interview still matters, but PMP is not just a piece of paper, it is commitment to learning it’s an achievement to get through 4 hours of exams and it feels great when you finally get it.
As for your second question in the exam you get an online notepad where you can jot down notes. I think its just a matter of preference if you want to dump the formulas onto it. I found the online notepad a little tricky so didnt use it.