1)
What is the meaning of "Titchan l'Acher Ishti"?
1.
Rashi citing Sotah 10a: It is an expression of Bi'ah, like "va'Yhi Tochen b'Veis ha'Asurim."
2.
Malbim: My wife will be a disgraced Shifchah who grinds with a millstone - "ha'Shifchah Asher Achar ha'Rechayim."
2)
Why does it say "v'Aleha Yichre'un Acherin"?
1.
Ramban: Others will conduct with her like Hefker, like with "ha'Shifchah Asher Achar ha'Rechayim." Ibn Ezra - it should say Acherim; there is a Nun in place of the Mem, like "l'Ketz ha'Yamin."
2.
Malbim: Others will be Mezanah with my wife, Midah k'Neged Midah.
