Joseph,
1. I think that the Jews in Teiman would have been very surprised to be called Yidden.
2. The Israeli Chief Rabbinate ruled that it is now minhag Yisrael to have only one wife at a time (@Milhouse, their authority is that of a bet din kavua, at least for Israel). In fact, the Mechaber says that the Sephardic ketuba has a clause prohibiting the husband from taking an additional wife without his current wife’s permission.
3. Someone I know told me that an Arab co-worker (he worked for a while in construction) bragged that he can have four wives. My acquaintance replied that that means four mothers-in-law.