It’s not easy to take care of a child who has autism.
First, it’s beneficial to recite the Great Compassion mantra and the Buddha’s name. Make sure to dedicate the merit and virtue on his behalf.
Traditionally, it’s better to receive transmission of that mantra before practicing it. Since you have affinity with Great Master Xuan Hua, you should go to a temple of his or his disciples to ask for transmission of that mantra. It’ll help with your recitation. They could also give you more advice on how to maintain mantras as well.
Furthermore, you should consider getting spiritual help for your child. You have exhausted medical help. It’s time to explore more spiritual help. While reciting the Great Compassion mantra is helpful, you may want to consider external help: professional help could be of immense value to you.
For example, the Chinese have the Medicine Master Dharma that will greatly benefit your child. You could get more information on the Medicine Master Sutra on our web site. Getting a Medicine Buddha plaque for the family will provide more protection and quicker debt repayment to your creditors who are clearly creating problems to your family through your son.