Thank you for your feedback! For the torch, the item under it should highlight if it is placeable, as you can only place it on flammable objects (bombs and fire.) For the other placeable items, they can be placed anywhere as long as it is not touching an object. All combinations of weapons were thoroughly tested and were able to destroy the entire map in all modes, so you shouldn't be running into that problem.
We're glad you enjoyed the game and appreciate the comment!