In those days, when a man came across a stranger, he would reach for his weapon out of fear in spite of himself with his right hand, in case he had to use the weapon to defend himself.
スラッシュは前置詞、接続詞の前、カンマの後に入れます。
In those days, /when a man came across a stranger, /he would reach for his weapon /out of fear /in spite of himself /with his right hand, /in case he had to use the weapon/ to defend himself.