Salary

So my employer says that I have to work any emergency and/or project related overtime without overtime pay. I can only exchange for additional PTO time. Equal exchange; hours worked= hours PTO.

I feel that I should at least get 1.5X PTO. Am I correct? Is this legal?

My paystub says that I get paid bi-weekly for 70hrs. Although there have been over 20 days this last year that I did not get paid. A friend of mine told me that my salary is capped at 70hrs bi-weekly and that I am legally obliged to overtime pay.

I can say that I work for a nonprofit in PA and non of these details are covered in my contract.

Any help or resources are greatly appreciated! Thank you in advance.