Does a conditional divorce, contingent on "if you wrong me in the future," become void if the husband divorces his wife and then takes her back, or does the condition remain valid unless it is fulfilled?

Since you intended to effect a divorce upon the fulfillment of the condition, it will occur if the condition is met. It will not benefit you to divorce your wife and then take her back during her waiting period ('iddah), because the oath is not dissolved by that.

However, Sheikh al-Islam Ibn Taymiyyah holds the view that whoever intended to effect a divorce upon the fulfillment of the suspended condition may retract the suspension, and there is nothing against him.