That does mean you don't have world bounds.
Do you use JNGP or the normla vanilla editor (The one installed together with wc3)?
In order to compile vJass code, you need a JassHelper. JassHelper is integrated in JNGP.
Dynamite.... change it into somethng fitting to LOTR theme or old style medieval theme like maybe Exploding Chemicals (it's a potion when throwed, same with yours, 3.2.1 and then it will explode with acid, damaging all units affected by it in a AOE and another continous damage.
It's good to know you're going to make a Cave Troll Fight, here are some ideas:
We all know that plain battle is boring so adding some traps and random triggered event could make it pretty much interesting, like at some points, dust would fall from above and then if you stay too long on the position, rocks will drop damaging you or maybe worse is killing you.
Another idea is that maybe Cave Trolls could start like an armless beast but it can get materials from the battlefield to serve as weapon like how Stone Giant works, doing so, you would need an armless unit and then just adding the attachment upon getting the material.