hey, how long have you had Damian?
My last syrian Sandie, would bit viscously if i put my fingers in the cage bars. But was a sweet heart if i put my hand in normally
I would have thought you just need to take it slow, give him treats when you manage to stroke him (reinforcing good behaviour), but not a lot of treats! syrians get funny with a change in diet, just one natural treat (avoid too many sugar high processed treats)
Hope thats of some help