1 tn The clause is a relative clause modifying “those things,” the direct object of the verb “eat.” The relative clause has a resumptive pronoun: “which atonement was made by them” becomes “by which atonement was made.” The verb is a Pual perfect of כִּפֵּר (kipper, “to expiate, atone, pacify”).
2 tn The Hebrew word is “stranger, alien” (זָר, zar). But in this context it means anyone who is not a priest (see S. R. Driver, Exodus, 324).