Hmmm. You say you have a frozen ATPL, but that's EASA language, meaning a commercial licence with all the ATP theory exams passed, in FAA land they don't use that misleading term, they just call it what it is, a commercial pilot certificate.
I'm sorry to hear Tunisia don't accept it anymore, they must have shifted to the EASA way of doing things recently. Whatever you do, don't waste your money on instructor ratings if you can't work in the US or Canada, it's bad enough having pilots certs you can't use. The schools will be happy to take your money one way or another.
You would be better off using it to build hours and go to Botswana or Namibia as 500 hours is the absolute minimum now for those places.