What are the connotations of "Al Teshaktzu es Nafshoseichem"?
Rashi (in Yoma, 80b): It is a prohibition against abominating oneself by eating Sheratzim.
Makos 16b: "Es" includes things that are disgusting - such as drinking from bloodletters' Keilim, 1 and Beitzim Muzaros (they are not from a male, but a hen sat on them for many days); if they are repulsive to people, one may not eat them. 2 Also someone who delays his bowels (and some add or urinating) transgresses it.
Seeing as only Kohanim are subject to the Isur of Tum'ah (See Emor, 21:1), why does the Torah write "ve'Lo Sitam'u bahem", implying Yisre'elim as well?
Rashi (in Yoma, 80b): Because "ve'Lo Sitam'u bahem" is a prohibition (not against touching Sheratzim, but) against eating them. 1
What are the ramifications of "ve'Nitmeisem bam"?
Rashi: If someone is Metamei himself by eating Sheratzim in this world, Hashem will be Metamei him in the World to Come and in the Yeshivah shel Ma'alah. 1
Yoma 39b #1: "ve'Lo Sitam'u bahem ve'Nitmeisem bam" - If one defiles oneself a little, Hashem will defile him a lot; if he defiles himself below, Hashem will defile him above; if he defiles himself in this world, Hashem will him in the world to come. 2
Yoma, 39b #2: We read this as if it had written 've'Nitamtem bam' 3 (and you will become spiritually insesitive), because sin blunts a person's heart. 4
Oznayim la'Torah: It implies that, over and above the La'av that one transgresses, there is a Tum'ah in Neveilos u'Tereifos, Shekatzim and Remasim that envelops the person ? even if he eats them be'shogeg and even be'Oneis, and which does not go away, even via Teshuvah, until one Tovels in Mikveh. 5
Even if he merits a portion in Olam ha'Ba, he will sit there in a state of contamination.
See Torah Temimah, note 197.
Since the Torah spells "Venitmeisem" without an 'Alef'. See Torah Temimah, note 196.
Mesilas Yesharim (Perek 11) - forbidden foods bring Tum'ah into a person's heart and Nefesh, and Hashem's Kedushah leaves and distances itself from him, and true knowledge, Ru'ach and intellect leave him. Chafetz Chaim (on the Sifra, Perek 6 Parshah 5, 1): Chazal extrapolated that the Pasuk is not discussing eating, since the only food that is Metamei through eating is Nivlas Of Tahor.
See Oznayim la'Torah, who elaborates at length.