Hi there,
Thank you for your responses. I think if there is a cavalry model behind rows of people, they are higher than the others so there is a probability to shoot them. However, as I explain before, in the hill scenary I can only see the hill and the cavalry (and one head of one of the soldiers) so I would make the hill and the soldiers as obstacles (If the hill wasn't there I should throw a dice for each row of people in front of the cavalry target). In the case of the Bolt thrower, a Light army can't attack if there is a possibility of injuring another ally so the machine can't shoot.
Finally, the forest problem it's difficult to solve: On the one hand, forests should be great allies for elven cloaks, but taking into account the rules, you can only benefit them if you are parcially hidden by a tree physically in the forest. We'll discuss about it each new game and we'll see.
Anyway, thank you very much for your helping hand!