My answer is in the image, but I'm not feeling confident enough to think I did it right, if I did it wrong, could I please receive an explanation on how to do it? Thanks.

First part (to find mMON) is correct.
To find mPON, we can't assume the angle has been divided into two equal parts; so we need to apply the same procedure as on finding MON:
tan⁻¹(2/6) = 18.26°