I'm here, but just a lowly earthling :)
Sorry, can't help with advice on amantadine. My main symptoms were (and are) poor gait initiation, poor balance especially when turning, unreadable handwriting (unless I use my "wrong" hand which is incredibly slow), fine repetitive hand movements out of control . . . I am on madopar, have been for about a year now. My consultant said at the beginning that gait problems are very difficult to improve with medication. I think mine are now very slightly better, but this maybe due to management rather than medication. I count in my head, tell myself "big steps" etc. But it all goes to pot when I'm stressed or preoccupied . . . the concentration required is very tiring too.
Not much help there . . . hope somebody else joins with some good advice in soon.