Sharmin,
We have had two kids in my centre, with a lot of the antibody symptoms and rapid haemolysis, similar to the symptoms of your son. The centre used to have a really, really tough time to cross-match the blood, and they used to get maybe one 80-85% match after cross-matching over 15 packets. Typical pre-tx HB used to be an average of 5-6gms. One kid even underwent the Ritux treatment for a month, or so.
After a lot of counselling (and entreaties and threats!), these two kids have had splenectomies done over the past quarter - I am happy to report that both are doing significantly better. The younger child has her pre-tx HB up to 9gms and more - not sure about the older kid, have not met her in a bit, but she was doing much better the last time I met her. And, the requirement of blood has dropped significantly.
So, this is an alternative that you should keep in mind, if the antibody issue recurs.
Poirot