I need advice

Recently I had to move back in with my mother because we were unable to keep up with bills due to me being fired for being pregnant I was told I was a potential liability ( I worked as a overnight stocker .) my husband kept up with his job but yeah just couldn’t cover our home sadly . Well now that we are here with my mom she keeps giving my son her phone ! He has autism and for the last two weeks she had given him YouTube for HOURS I explained that this is not good for him or any child especially him he just began to speak and tell us what he wants etc but has regressed tremendously due to her babying him and giving him YouTube . I asked her nicely three times to stop giving it to him . She says it’s educational but he has educational toys and activities you can do with him instead of giving him YouTube . She didn’t even allow us to watch TV but will give him YouTube and Her phone .Today as soon as he woke up she gave him the freaking phone I had it and snatched it from her and told her you will not be able to be around my child unless you can follow my rules . Now I have been respectful for weeks because you are my mother but he is My Child . I am literally out here cleaning etc and now that I am on my last week of pregnancy I am xtra busy with my OB appointments, his speech and occupational therapy on top of ABA therapy and my appointments with MFM . She literally asks to spend with him when I have an appointment to go to and I allow it just to find him glued to the tv when I get back . He is now whining and crying . Not talking acting like a baby . Throwing tantrums something he stopped doing back in April he has been talking since august of last year . I am moving out next month . But this is fcking stressful what can I do not to loose it . He is 53lbs literally drops to the floor and has tantrum or tackles me I can’t even lift him up . She is making my life hell right now