Gameplay tactics on the large map.

Yeah, in this case, the AI calculates very accurately and doesn't just let you run away; it positions its units so that it can always reach you.
It's really difficult to break through with 60 Warriors on the third day. The hero isn't leveled up yet, and he can only take down two of them at a time, and he only has enough mana for two spells. So, for the Tower, this is a real bottleneck.

There are taverns available on the first turn, but if you try to build both a Hunter's Hall and a Mercenary Guild, you won't be able to build one of these alternate upgrades due to the lack of ore. And you're wrong about the Warriors; try placing 60 Warriors, divided into 3 stacks, against 9 Beasts, and they won't let you escape and will kill you.