My milk had the same attitude when I got it. I think holding it when it is least active during the day helps (I don't remember if corns are nocturnal or not). Also I noticed that when holding it while it was in blue, I know people say you're not really supposed to, it was less likely to do the suicide jumps and it didn't move around as much. It probably appeared to be less stressed out but it really was more stressed...
As for stroking it, it's probably not helping, it's just annoying it. Just make as little motion as you can around it. I think moving slow gives the best results, at least it's slowing down on the biting too.