1)
What are "Tzefi'ei"?
1.
Rashi: They are dung. Radak - this is like Tzo'eh, which refers to Yetzi'ah (leaving) the body. Also Tze'etza'im (offspring) is based on Yetzi'ah.
2)
It is written Tzefu'ei, and we pronounce it Tzefi'ei!
1.
Radak: Aleph, Hei, Vov and Yud are interchangeable.
3)
What is the significance of giving cattle dung in place of human excrement?
1.
Radak: Cattle dung is less repulsive than human feces.