I can see many many things that can go wrong with all stages of your plan,
no part of the plan replicates successful recovery programs,
Which would be fine, because you could then try again with different methods,
Except you are locating the vital part of the plan in a country that has a death penalty for drugs, because drugs are so readily available.
the place you have chosen, has had people flee and get into serious difficulties, there problems that come afterwards when returning to home environment,
please get some specialist advice, and I recommend that you find a funded program here that provides ongoing support which will insure it is a permeant solution, where medical support is available,
any travel insurance you try to take out will be invalid as if you don't declare the addiction, it won't be valid should you go to claim,
I understand the desperation, and the lure of what appeals as solution,
Sometimes when a love one is endless hopeless addled addicted life, it's easy to latch on to what seems one stop wonder to end something that dominates the whole of family life.
please please get specialist advice, you may not like what you hear, it's frustrating, but you all need to go and really listen to how best to help your BiL.