pku disease

My son has a late diagnosis of pku like disease, the inability to breakdown a certain protein in foods. Initially he was diagnosed with autism when he was 3yrs, through blood test 4 months ago it was found that he can't break down protein in foods. His now 8yrs can not talk. His very tall, loves music with happy beat, he loves to climb and jumping of high things, grind his teeth and his still in nappies. He eats very well. Mentally his function at 8 months, he hates washing or cutting his hair, rocks back and forth and loves blankets. He does not interact with his friends and his zero social skills, no sense of danger and when he take him to public places he runs off. He alse like humping things and touching his private parts. I have already put him on a low protein diet. I can not afford the pku medicine as am very poor. What homeopathy medicine is good for treating this disease. Thanks.