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.
You were not wrong in asking your husband to provide you with an independent accommodation because the wife has the right to ask her husband to be in a separate dwelling that suits her and where she does not find any embarrassment.
For more benefit, please refer to Fatwa 86388.
The fact that he does not want to leave his widowed mother alone, does not mean that he has the right to wrong his wife and prevent her from her right; rather, he should give everyone his right.
It is acceptable that you have a separate dwelling even if it is in part of the family home.
With regard to your saying: "My husband divorced me on the phone three talaaq (divorces) at once…”; it is a general term. It is probable that he combined the three divorces in one word i.e. ‘you are divorced thrice’ in one expression. Or that he repeated the expression and said to you: ‘you are divorced’, you are divorced’, ‘you are divorced’; or that he said this while combining them with the conjunction ‘and’ for example [you are divorced, and you are divorced and you are divorced].
It is also probable that he repeated the information and said: ‘you are divorced, divorced, divorced’. Each expression among the three different cases above has its own ruling.
In some of it, there is a need to know the intention of your husband, and whether he intended to issue a new divorce by repeating the word, or that he intended to confirm what he said by repeating the word.
For more benefit, please refer to Fataawa 82330, 155573 and 94110.
As regards the case when he wrote the word divorce, then writing the word divorce is one of the metaphors of divorce and divorce does not take place unless the husband had intended it as we have clarified in Fatwa 174947.
As you see, there is a need to know exactly what your husband had said in the first case, and to know the intention of your husband in both cases, in addition to the existence of difference of opinion among the scholars on some issues.
So it is more appropriate for your husband to consult an Islamic court in order to clarify to them what he had exactly uttered and his intention, and the judge would ask him about what needs details. He may also ask orally some scholars if he does not go to the court.
If the judge or the scholar issues to you a Fatwa that you can return to him, then do not take into consideration the view of the society. So, in this case, just return to him and each one of you should have good marital relationship with the other and avoid problems as much as possible in order to maintain the cohesion of the family, and that your husband avoids solving the problem by divorce.
The problems between the wife and the mother in-law, is something that happens a lot. So both of you should be wise and have an understanding so that you may overcome the problems without having a negative impact on your married life.
It is a bad marital relationship that the husband beats his wife and abuses her, as this is an injustice to her, while he is ordered to have good marital relations with her.
Allah Says (what means): {And live with them in kindness.} [Quran 4:19]
Allah knows best.