I think you need to add a new vocab category to this part maybe?
# This adjusts the settings shown for equipment. Adjust as you see fit. For
# :shown_stats, valid stats to be shown are as follows:
# :hp, :mp, :atk, :def, :spi, :res, :dex, :agi
EQUIP_DATA ={
:properties => "Attributes",
:gold_value => true,
:fontsize => 16,
:shown_stats => [:hp, :mp, :atk, :def, :spi, :res, :dex, :agi],
:ele_weapon => "Adds",
:ele_armour => "Guards",
:state_weapon => "Applies",
:state_armour => "Resists",
} # Do not remove this.
I'm not 100% sure though as I'm not a scripter.
Personally, I'd upgrade to Ace. YEM isn't supported anymore and Yanfly's Ace scripts improve on pretty much all of his VX scripts.