50mm 2.5 macro - a good portrait lens?

You are describing close up portraits that only fit the face in the frame.  For those, you want a longer focal length and a narrow aperture.    When many people talk of the "ideal" portrait lens, they are referring to waist-up or full body portraits with nicely blurred backgrounds.   For that a 85 or 100mm fast prime would be excellent.  It's just a matter of the type of photo you are taking.

If you want a flattering self portraits.  Set up the camera on a tripod and sit on a stool 8 feet away.  Focus on a stand in object and then set the timer or use a remote.   Handheld self-portraits will ALWAYS have perspective distortion.