im not sure is this can work or not but i suggest
BURRIED THEM ALIVE
with one hollow pole or air tube to give them hole to breath and eat or drink, im not even sure you need coffin for them.
since you say they can control 2 ton at best just dig deep enough to surpass 2 tons.
this will bind their body in place, cant struggle, or see, all they can do is shout and its better that they dont.
here a movie that depict the feel/horror of being buried alive Buried and this video Buried alive (so i doubt someone can still feel rage or hatred because such behaviour wont save them, and they more likely get traumatised instead, which help in manipulate them to be obedient) and even if you can punch through the coffin like in this movie kill bill 2 i heard including myth buster, realistically the soil that come through should have suffocate or crush her instead. (example like from this link)
also depend on the dirt or field density i think you can remove the pole if you consider it dangerous while keeping gap of hole in the dirt. but if he dare to move his tube or pole it mean he just lose the hole for him to breath and enjoy his burried life.
also as soon the guard feel the hostility they can torture them by just pouring anything hot into the hole or just cover it to make them unable to breath, or just leave them burried like that for long or forever that kind of thought will increase their survival instinct or trauma and have more chance for obedience upon release, if they goes mad then its easier to end their life and not require to make new burrial so it cost effective and simple and cheaper doesnt require industry method to create huge amount of metal.
theres also no way to get out or door to open except tiny hole for the pole which wont be enough to pass through nor dig out of, and any movement to it will only result of the soil to crumble and filling the coffin or their mouth, and worst case it can result in plugging their only hole to get oxygen, unless the dirt or soil is taken out they wont go anywhere.
regarding evacuating their bowels/bladder they can just do their bussiness there, they are prisoner after all no one care about sanitizing regarding jail anyway. it even better to torture their dignity and comfortability, i also doubt there will be a big pile of poop and piss if the guard give the prisoner food to barely enough to make them stay alive.
reasons i suggest this
if you dump them to far away desert islands like australia or alcatraz theres no guarantee they wont build their own kingdom like australia or create flying object or any transportation to invade back.
just put them in a hole or pit without any roof or an exit in the roof doesnt guarantee they dont just dig it out from other place or find material to fly off (since it have no roof chance for outside material to be possessed is big like from intruder/spy)
putting them in cell with impure material doesnt change that you can picklock or manipulate with viewer pure material or smaller controlable impure material to open it or corrode it from acid like piss,sweat,or create salt from your body, or doing similar principle like water breaking a rock.
and especially if you put them in group will only result in disaster.
drug is double edge sword it doesnt guarantee rival kingdom or the people that not captured wont grow their own drug to sway them over, besides its not like drug is irresistible they can just resist the urge by sheer will or hatred alone and just pretending to make an opening to revolt.
just because the people can or cant use telekinetic it doesnt mean they cant use their body parts to manipulate object.