1- After learning of her husband’s temporary marriage, can the wife ask for divorce? Isn't this act of the husband considered being unfaithful?
2- Is there a center or place where one can put into practice Islamic laws through temporary marriage?
3- What is the main reason why women oppose both temporary and permanent marriage of their husbands?
1- According to Islam, the man can choose more than one wife, or practice temporary marriage  , without the wife’s consent being a condition.  Therefore, such an act isn't considered not being faithful or cheating on her, and the wife has no right for divorce after such a marriage has been consummated, because divorce is at the hands of the man in Islam. Of course, the woman can always ask for it, but this doesn’t mean that she has the right of executing it.
2- As for their being a center for such a thing, there are none that we are aware of.
3- Psychologists and experts say that there is an essential difference between the mental structure and inclinations and emotions of men and women. They believe that women are naturally monogamy inclined and resent having more than one spouse and like to be supported mentally and practically by one man. Men on the other hand, are essentially polygamy inclined.  On this basis, it can be said that their opposition with re-marriage of their husbands mainly has to do with their feminine nature, which of course can be moderated, because as you know, there is a difference between one’s nature and fitrah; fitri matters can be increased or decreased but can't be uprooted, as opposed to natural tendencies and desires in humans. 
For further information, see:
1- Temporary Marriage of a Married Man Without His Wife’s Permission, Question 7686 (website: 7761).
2- The Problems Faced by Practicing Temporary Marriage in Society, Question 6146 (website: 6348).
 It is because of this that the ulema have said: Women cannot prevent their husbands from exercising this right. Imam Khomeini, Istifta’at, vol. 3, pg. 100, question 55.
 Mutahhari, Morteza, Majmu’eh Āsar, vol. 19, pg. 302.
 For further information, see: The Fitrah and the Impermissibility of Music, Question 1078 (website: 1256).