I'm pretty sure there are no clear cut answers to these questions so not really interested in starting a debate about rule interpretation, just want to find out how it is most commonly played.
(1) - can you hit more than one model per rank by aiming diagonally?
(2) - do characters get a look out sir roll if hit?
(3) - can you choose a direction which could hit a unit in combat?
1) Yes, Use the edge of the a tape measure.
2) Yes, The line in a "templete"
3) Yes, The FAQ removed the 1st line.