A good idea to make this weapon balanced and only interessting for Horse-Use is to make it "unbalanced".
It wouldnt be a good idea to use it on foot but i guess it doesnt really matter if a weapon is "balanced" or "unbalanced" if u use it from horse.
At least im still waiting to see some Horseman feinting with his weapon :p
My Proposal is:
3.50 weight
14 difficulty
87 speed
102 reach
28 blunt
8250 gold
Unbalanced
Knockdown
PS: I cant see your textures very well cause your screens are so dark. cant you make a brighter picture with more light.