She's simultaneously not safe in the community and suited to mainstream school?
There's a special needs board on MN (you've posted under parenting generally) - the special needs board might be a good place to find support and practical tips, both for your school appeal and carers appeal.
It's exhausting and unfair that when you're dealing with so much you have to do more in order to access any help, but it sounds as though every member of your family - you, your daughter, your autistic son and your neurotypical son, will all be much better off when your daughter is in an appropriate school (a special needs school school be able to help her learn coping and communication strategies, offer suggestions for simple tools and aids and generally improve her quality of life) and you have carers back in place if at all possible.
It's too much to think about all at once, but it may be that she'll need a suppoted living group as an adult especially as she's already too much for you to keep safe outside the house. You need a bit of time where she's safe at school or with carers to start looking into that.
There is no medication "for" autism to help her cope, though a lot of Autistic people (especially those with co-occurring conditions) are on lots of medication for those co-occurring conditions. In my experience even people on very high dosage of quite hard core medication still have episodes of behaving as your daughter does, if that's been normal for them previously.
Medications can help with anxiety, depression, psychosis where relevant, other co-occurring psychiatric disorders, and obviously is necessary for epilepsy which is a massively common co-occurring condition in the Autism with learning disabilities population - and short term can help somewhat with overwhelm, but they won't stop her running around screaming if that's a maladaptive strategy she's developed to cope with overwhelm/ frustration/ other triggers.
Have you ruled out pain or digestive distress and any pattern of behaviour around her menstrual cycle? Those can all be triggers which can be addressed to a degree.