絕望: My son is diagnosed with RP - Please Help!!!

My 7 years old son was diagnosed with RP (Retinitis Pigmentosa) at Beijing University Medical Center in China. I showed his exam results to the opthalmologists here in California and was told that my son will be blind by the age of 20. I am heart-broken...

Symptoms:
1. Slight difficulty to see at the night;
2. Severe reduction of the field of vision (Less than 30 degree now). Only center vision now.
2. Nearsightedness: 0.2 and 0.1 in both eyes. Corrected vision w/ glasses: 0.9 and 0.8 (200 degree in classes)

Family history:
1. My mom and my maternal grandpa (and his sister) have RP.
2. My mom's other 5 brothers and sisters (and their children) are normal.
3. No other family history on either side.

Questions:
1. Anything I can do to save his vision or delay the time to be blind?
2. Should I bring him to the US for diagnosis and treatment?
3. Can I donate one of my eyes to help him? I know that it is a silly question, but I am the mom... Does eye or eye tissue transplant help RP?
4. Will it help if he start to take Vitamin A? How much should be the dose? 15,000 IU or 1,500 IU? I heard that high dose of Vitamin A may have severe side effect on young children.
5. Any other suggestions?

Thanks a million!!