As with the belongings question earlier, combat positioning is not strictly governed by these rules, but is definitely a part of the world. A lot of these problems you propose will be solved when you describe the scene and use common sense to adjudicate from there.
So for example, if a party encounters a group of goblins, imagine the situation and describe in simple terms where the goblins are standing, what the area looks like, which characters can reach each other when they move towards each other and which characters can be hit by the characters using ranged weapons. If you want, you can sketch out a simple battle map on a piece of paper and use tokens or miniatures to represent the characters.