Can you add 1D to your disposition roll if you have a sword in a fight conflict?
No, gear does not improve Disposition in a conflict.
Sword adds +1D to your choice of action (meaning Attack, Defend, Feint, or Maneuver) in a conflict, but does not aid any other rolls. [DH p159]
Each ally in the conflict may give +1D each on the disposition roll by Helping with a skill related to the conflict type (Fighter for Kill or Drive Off) [SM p68]