That means he no longer crits on a natural 16, cant fight with two equal-sized one-handed weapons and no longer fumbles only when both dice come up a 1?If the halfling has an Agility higher than 16, he instead uses the normal two-weapon fighting rules for his Agility.
I think it just uses the Dex 18's action dice but keeps all the other abilities.
Btw, I think the rule should contemplate that Dex 16 and 17 provide the same set of actions dice so a halfling should be considered to have a minimum Agility of 17 when fighting with two weapons.