Contact his local police force and ask to speak to the community officer for his residential postcode.
The local police can help him to secure his home, they can arrange for a panic alarm to be fitted, he will be given a personal attack alarm and they can help him with window/door locks. I know it sounds futile but it might help him feel more secure.
In relation to the actual crime, there is no point pressuring him to report it to the police if he does not want to, it is a very frightening prospect.
But there is legislation now to protect disabled people. Disability hate crime is categorised similiar to race hate crime or homophobic hate crime and the police have to take the matter very seriously and specialist support is out there.
I would advise you to take a look at the CPS website
http://www.cps.gov.uk/publications/docs/disabi lity_hate_crime_policy.pdf and rm yourself if the facts and responsibilities before you speak with your friend again.
Perhaps you will be able to persuade him to discuss the crime itself with the police and make a complaint based on the fact that he can withdraw support later if he truly needs to.
Also,
If you are successful in convincing your friend to act, then try and make sure you get a police officer who knows the score. Trouble is, many local bobbies don't know the first thing about this legislation.
If your friend decides to make a complaint, try and arrange to speak with a manager and explain your friends disabilities and the concerns you both have, or ask for a representative from the Hate Crime Unit (or equivalant) to be present when he gives his statement, that way they can tailor the support for your friend according to his needs.
I cannot tell you how sorry I feel for both yo