Hello Nannie, it is a terrible time you are having no wonder you feel ill. Caring is hard enough without it being to a child with special needs and then there is the fight between you and your daughter which is bound to make you ill. She is your blood after all, how hard this much be.
As a cArer you will have a Carers link in your area hopefully who can support you with having an assessment for your right to respite and other things even financial in some cases. Does your surgery have special support for Carers. In my area Devon, we can also have free counselling for Carers unlimited, which would benefit you enormously.
The eating has to stop Nannie, as does your grandsons. Think about his health, try to be strong and every time you do not eat healthily, think about the damage it does to yo and to him. Set a good example with ocassional treats. You can do it, the first couple of weeks are hard, but then it gets easier. If you can't do it on your own, ask your doctor for. Referral to a dietician, OT enroll with weight watchers you can even do it on line, but better to go to the meetings for weigh ins to be stimulated to carry on. You will have lapses, but get back on track.
Please, please do this for your grandson and yourself, it will in turn give you much more energy to fight your daughter and the authorities.
Seated exercises are very beneficial if you cannot cope with full exercises. You can see them on YouTube or there should be a Class in your area, age UK RUN THEM in most areas.
I really wish you all the best and hope both you and your daughter one day will bring up your DGS in unity supporting each another instead of fighting. Xx