Possible meanings are 1) he took aim to shoot a soldier without knowing that it was Ahab or 2) he drew his bow to shoot without any specific target in mind.
# between the joints of his armor
This is a place where two pieces of armor meet and is susceptible to arrows and swords.
# the king of Israel was held up in his chariot
This can be stated in active form. AT: "someone held the king of Israel up in his chariot" (See: [[rc://en/ta/man/translate/figs-activepassive]])