In my last role I supported a high functioning 18 year old to go to a private residential college as that would have been amazing, supportive staff, beautiful grounds and so plenty of space, lots of activities. I was so excited for him. The cost to the local authority would have been over £100k a year. It went to court and the LA argued his needs could be met in a autistic residential semi detached home with 4 others even though they were in their 40s to 60s, so no other young people.
That place was just over £1k a week and staffed by people who could not speak English well, with minimal training.
The lack of availability is down to cost. The lack of staff mean agencies are used to fill the gaps, so there are, for example night staff who might not know the people in their care.
Those living in sheltered accommodation in the community are often very vulnerable to exploitation and cuckooing ( where those who prey on the vulnerable often have substance misuse and move in and demand money etc).
The system is not ideal because we live in a market economy where services for those in need of care and support are costed. There is a limited governmental budget only covering the bare bones, no wonder it is a struggle for anyone caught up in it.
I argued for this young man's case because I could see it would have been in his best interest but LAs only have a duty of care as far as AVAILABLITY is concerned. So they don't provide spaces because of the sheer cost. One social services manager explained that they had a limited budget, and funding 1 place at a residential college would deprive others in similar need.
So you get where they are coming from.
There are residential places for child sex offenders with autism who live separately in a house with round the clock care and a staff of 4 -5 just for that one individual. You can see that councils don't have it easy either .
Staffing can be a nightmare. The op is thankful that her Ds is safe and only an hour and a half away is is lucky. Some DC are placed halfway across the country.
I am not sure what an ideal solution is.