What is "Mishpat ha'Kohanim"?
Rashi: They made this law for themselves. The Torah entitles them only to Chazah v'Shok (Vayikra 7:31-34).
Mahari Kara: The Torah says that a Kohen receives the foreleg, jaw and stomach. 1 They made a different law.
Malbim: It was not Mishpat Hashem, rather, a law they established for themselves.
Indeed, the Torah calls this "Mishpat ha'Kohanim" (Devarim 18:3), but that is for a Chulin animal. What is the relevance to Korbanos?! (PF)
Why does it mention "Na'ar ha'Kohen"?
Malbim: This was a disgrace, that they did not take by themselves from Hashem's table, rather, through unruly, wild slaves.
Which meat did they take?
Radak: In addition to Chazah v'Shok, they took from the rest of the Shelamim, which belongs to the owner.
Why does it mention that the fork had three prongs?
Malbim: They would take three pieces (limbs). This is a large amount that the owner does not pardon.
Why is Shinayim written with only one Yud?
Radak: It can be read Shenayim (two), even though it had three teeth, because the teeth of people and animal are in pairs.