If you want your son to have an idiot for a father, than call the police and report your ex for pouring acid on your son.
It is contact dermatitis, and I have been trying to be useful, but you are an idiot who is looking to screw your ex.
Unless you have dealt with special needs children before you should back off. Autistic children have a hard time describing feelings like hunger, of fear let alone understanding how some marks magically appeared on their body.
jiminy crickets! will you please shut up!?