To whom is "Kinyan Kaspo" referring? Why is he different than the Eved in the previous Pasuk?
Rashi #1: It is referring to an Eved Cana'ani, whose body the owner acquires, as opposed to the Eved in the previous Pasuk, whose body he does not acquire.
Rashi #2: It also refers to the Kohen's wife. 1
And to whom does "Y'lid Beiso" refer?
Rashi #1: It refers to the children of the Kohen's Shifchah Cana'anis.
Rashi #2 (in Nidah, 43b): It refers to the children whom the Bas-Yisrael bears from the Kohen who died before the birth, and who subsequently permit her to eat Terumah from the moment they are born. 1
And we expound the word "Heim Yochlu be'Lachmo" to read "Heim Ya'achilu be'Lachmo".
Ula (Kidushin 5a) expounds "Kinyan Kaspo" to include his Arusah. Sifri learns this from "Kol Tahor ['b'Veischa]" (Bamidbar 18:13)!
The Sifri says that she eats only after he acquires her earnings (Nisu'in). Ula teaches that this is an Asmachta, for mid'Oraisa, even an Arusah eats, for she is Kinyan Kaspo. Perhaps Ula relies on the Sifri, i.e. to learn that Kesef makes Kidushin. (PF)
The Sifri expounds so on verses 18:11,13. The former discusses parts of Kodshim Kalim given to Kohanim, and the latter discusses Bikurim; RS"R Hirsh (there) explains that the Drashah applies also to Terumah (taught in verse 12), for Bikurim are like Terumah.