I think
@AwayWithTheFairies is right about the lack of a garden probably not meaning much to someone with dementia.
My mum pre-dementia loved her garden, tended it and it looked beutiful. When dementia arrived she started to neglect it and by the time she moved into her care home she just wasnt interested in the garden and didnt even want to go and sit out in it. I noticed that none of the other residents did either.
I also wouldnt worry about the neighbourhood. I doubt that where it is situated will make any difference - its not like the neighbours are likely to pop in for a cuppa!
No place is perfect, but at least there will be a whole team of people looking after him round the clock.
You cant go on as you are, but a care home is probably the only solution; medication cant improve things and he cannot improve himself. Its easy to think "if only............ then I could ecope", but its not going to happen, is it?