Dyan
As long as you are sure that he will reasonably score the extra points then all he has to do is to write to the DWP office dealing with his claim and tell them that his conditions have deteriorated. I would recommend that you send it using a tracked post so the have proof of when the DWP receive the letter as this should be the date that any award is made from.
Be aware that he will receive a new PIP2 to complete and will almost certainly be required to attend a face to face assessment.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems