Adults with dyslexia can get help with specialists to improve their reading skills, although you cannot always find such specialists in all parts of the country.  Some tutors and speech/language pathologists have the skills to help adults like your son, as do reading specialists.  You might check with a local college disability support service for potential resources.  The book Overcoming Dyslexia, by Sally Shaywitz, who is a researcher on dyslexia, has information about adults.  Regarding your son and his wife, I would recommend counseling, so that his wife can understand his problem and have more compassions.

Dr. Mapou has presented very sound advice.  I would only add that you might help your son research remedial reading classes offered through a local library, community college and community education programs.  If your son is able to access the internet, he can also Google "free reading instruction; free writing instruction, free math instruction (free addition, subtraction, decimals, multiplication, fractions, money, time, etc.)" and an endless list of websites and resources will pop-up.  I also agree that your son and daughter-in-law would greatly benefit from counseling.  Unfortunately, it is not unusual for adults with disabilities to choose spouses that have little to no understanding for their challenges.  The low self-esteem of an individual with a disability too often leads to a poor choice in a life-partner.  Your son deserves compassion, understanding and help with his learning disabilities and not the ridicule of those he holds near and dear.  It was kind of you to post on your son's behalf.  Perhaps you can convince him to check-out Friends of Quinn.  He just might find the community he has been looking for. 

This is a very complicated situation. You should try to find adult night classes geared toward individuals who are leraning disabled so that your son can continue his education. As for his marriage, this is the last thing he needs. She obviously knew what his problems were when she married him. And there could be problems in the marriage you don't know about. Obviously he needs counseling but more than that he needs love and support. Without that it is very hard for anyone, child or adult, to succeed.