Why 『衛護』's 『護』 is 言部？
我想"衛護(wèi hù)"的"護(hù)"是由"辨護(biàn hù)"演变而来的。I think "護" in "衛護" is derived from "辨護" (verbally defend) and hence the 言 radical. This is what I found on 汉典:


  清代段玉裁『說文解字注』
  
  救視也。尚書中握河紀。堯受河圖。伯禹進迎。舜契陪位。稷辨護。注云。辨護者，供時用相禮儀。周禮注亦云辨護。蕭何世家。數以吏事護高祖。从言。蒦聲。胡故切。五部。


(Sorry, I can't decipher the full text for you. Maybe someone else can help to explain what it all means.)

"衛護(wèi hù)" means to protect or defend, so you are right to point out that 言 radical should be changed to ⺘radical instead. This is reflected in the new 简体字 "卫护".

"擭(huò)" wasn't used as it possesses the meaning of capture:


  清代段玉裁『說文解字注』
  
  搫擭也。从手。蒦聲。一虢切。古音在五部。一曰布擭也。此卽今之布濩字也。劉逵注吳都賦曰。布濩，遍滿皃。一曰握也。握者，搤持也。西京賦。擭獑猢。薛云。擭謂握取之也。今本握譌掘。玄應不誤。