First of all, I want to wish you all the best danfrog, and your little frog too. I realise your going through a rough time, but hang in there, this battle isn't over yet, Gingerbread is clearly showing fighting spirit!
Couldn't the stiffness in the arms point to a calcium overdose? Since if looking at it logically, too little calcium makes bones fluid, so too much could cause stiffness in them?
I know you allready know this, but I'l mention it again. I'm not an expert, but I have high logical thinking. Note that too much calcium can also cause constipation in humans.