Wow! What a sad story. I fully understand his anger but he did not have the right to treat the child badly because of it. It wasn't his fault but his wife's fault! Now if he decided to forgive his wife and stay then he needs to treat this kid properly, just because he just found out that is not his literal son, does not mean he must now put him in an institution.
The story ended with him accepting him. He did not treat him badly, he spoke to him harshly in the museum because he was overwhelmed with frustration. This boy was so socially disabled that he would not look at people in their eyes and often hid behind garbage cans, under cars and so forth to be isolated from noise and everyone else. I believe that would frustrate anyone.
Yes, most autistic children do not make eye contact and the reason they run away from noise or people is that the environment is very sensitive to them and noises causes them great pain.
I am glad to know he accepted him, when you think about all the challenges these kids go through with not fault of their own, really breaks your heart.
Effects of supervision variables in treating ASD
Scientists have announced study findings on the effects of variables in treating autism spectrum disorder (ASD). The evaluation provides the most up-to-date, scientifically sound evidence to CARD and other autism therapy specialists in order to provide the best treatment to those with ASD. Ref. Source 6i.