The only website I can think of for help, is the CF Trust website- www.cftrust.org.uk. They have a large number of members on there, who may have the same mutations, and can provide more info with regards to symptoms.
I've heard of some people not having the enzyme problems associated with CF, but not without the chest problems. However, some kids don't even get a chest infection until they're 15/16, no matter what the mutation. Meaning they don't have many chest problems, as there aren't any infections to cause lung damage. My little brother was one of these kids. I wasn't. Both of us have 2 copies of DF508, and there is a lot of difference between us healthwise.
The different mutations cause the CFTR protein to act differently in different parts of the body. I have no clue what those different parts are in the mutations your son has.
Sorry I can't be anymore help