1. Essentially, you need to apply to the court of Protection to be appointed a Deputy to manager your son's affairs. In that way you will have control over his affairs. There are 2 types of deputies:
There can be more than 1 person appointed as deputy to each type. I would suggest that both yourself and your wife seek to be appointed Deputies to manage your sons affairs. In that way, if one of you dies or is ill, then the other can carry on dealing with your son's affairs.
2. If you are appointed as Deputy to manager your son's property and financial affairs, then you will have control of the money coming into his account and will be able to handle his outgoings, thereby you will be able to ascertain where his money goes. It will also give you greater ability to decide the appropriate care for your son and will help you in seeking a move to another care home.
3. Here is a link to the Government website which will assist you in making an application to the Court of Protection https://www.gov.uk/apply-to-the-court-of-protection . You will need to download the relevant forms and submit them to the Court along with the relevant fees. The Court of Protection will then approve your application or not.
4. If you require any further information I will be happy to help.