EB-1 seems a trifle optimistic, who told you this was a good idea?
It appears you are currently out of status and deportable so should leave as soon as possible.
Who mentioned negative rate, well unless you mean the effects of inflation, think that is about 4%.
No different to investing in a say a Government bond which pays 4 ish % and using that income to buy lottery tickets.
My first thought is that this is very generous of you, I can only imagine the cost.
You have a school lined up? Have you spoken to the International Admissions Officer?
I have not heard of this, I do know that getting a Polish visa for tourism is next to impossible. Turkey seems a popular destination and can personally recommend it.
Just a quick comment he is from the UK and no mention of needing to go to Europe.
Obviously the personal issues we do not know, I think it is fair to say most people would adjust. 18 months or so is a long time but then again we do not know what he needs to finish off if anything.
Sadly I assume many people forget to mention them, obviously you need to do so and if memory serves me the interest is tax free in the UK but not the US.