Falcon Fists gloves have following mod:
+(12 to 16) Cinder Strike Melee Damage per Level of Falconry While Unarmed
The damage is added only for Falconry levels 1-20, damage from any items that give additional Falconry levels is not added. Damage of Cinder Strike is the same for Falconry level 25 and 29. Checked on training dummy, tooltip also does not change.
I would expect from the item description that the damage from additional Falconry levels to also be added.
Of course like the description says - no weapon in main or off hand.