Sue
It certainly is a roller coaster ride in every sense imaginable!
Glad your OH is through 4 treatments now, they would not have proceeded if his blood work was out of limits.
The arm aches are a common SE, well aches anywhere are to be honest.
If his bloods are a bit low in areas they nay give him a transfusion of red cells or plasma these really do give a boost to well bring for a while and can be repeated fairly regularly. Is your OH having Zometa or Denusomab to try and provide bone strength?
Make sure you take good care of yourself as well.
All the best
Xx
Mo