All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If the exact words that you uttered were as mentioned in the question, “I divorce you” in the present tense, then divorce does not take effect as stated by scholars, because the present tense could denote the present or the future, unless you intended by your words to issue an immediate divorce or it is common in your community that using this wording of divorce denotes issuing an immediate divorce.
Assuming that you intended to issue an immediate divorce or it is common in your community to use this wording for issuing an immediate divorce, then if you intended to confirm the first pronouncement of divorce by the second and third ones, then those all count as one single occurrence of divorce. If you did not intend to confirm the first divorce therewith and rather intended to initiate a new divorce by uttering each of the second and third divorces, then those count as three occurrences of divorce according to the opinion of the majority of jurists. Shaykhul-Islaam Ibn Taymiyyah and other scholars, though, held that it counts as one divorce only. Perhaps the person who gave you the Fatwa that only one occurrence of divorce took effect in your case relied on this opinion. So, based upon this opinion, your marriage bond is still intact, and it is incumbent on your wife to obey you and return to the marital home, and her parents have no right to prevent her from doing so.
We advise you to seek the help of your Muslim brothers in the Sharee‘ah Council or the Islamic centers to try to persuade her parents. Otherwise, you may refer the case to the court if needed, because it is permissible to refer disputes to civil courts run based on man-made laws in case of necessity.
It is good that you learned a lesson from what happened, namely the danger of ignorance and the importance of knowledge. We advise you to protect your family and work with your wife to maintain its stability. You should beware of rendering divorce the first resort to solve your marital problems. Instead, you should adhere to deliberation and wisdom.
Allah Knows best.