Sparkly, if you are trying to build up a police log, and you've already contacted them about the assaults and intimidation, then you could call the police about the car too. Whilst ordinarily, with no further info, they might think this would just be a case of two neighbours having squabbles, if they've got your record of incidents, and are made clear of your fear of going outside, and the threats on life etc. they will liaise with neighbour to get car moved.
I can understand how this can make the situation worse, sparkly, and you know I would never wish that upon you, but you only have a few choices:
Leave car where it is and remain feeling prisoner in own home till apeman decides to move it.
Talk to apeman and ask him to move it (which would probably be best as he will either do it or create another event for you to log with his verbal....)
Get the police out to do the talking to neighbour / force him to move it.
Another point: You say you have spoken to the parents of apeman with whom I believe you enjoyed 5 years of good neighbourliness... they sound reasonable. Have you spoken to them to outline clearly the extent of abuse / threats you have received from their son and his ape-mates ? I'd imagine that if they were reasonable, despite ape being their son, they would kick him out and tell him to sort himself out... because if the police / council get very involved, they may risk being evicted.
I know you've been in contact with lots of housing people / council people... can you confirm where things sit with the other agencies: police and GP ?
Finally, ref hostel: Of course it is never what you would want, but from my barest of understanding about the points system for calculating housing etc. it may be of benefit if you are in a hostel in order to get a decent place after that, IYSWIM. You were briefly on a thread which discussed this here . Have a re-read... might clarify things a bit ?