As to looting the gold, gold alone doesn´t buy weapons. Hitler would need to find a middleman who is ready to buy the looted gold and buy/resell the things Germany needs. Switzerland, and to a lesser extent Sweden, Turkey and Portugal, fulfilled this role. But none of these countries (with the possible exception of Sweden) was under direct threat of German army - so they could, theoretically, just say "gold? what gold? You didn´t deliver any".
Switzerland was not just a neutral and a middleman - it was the only middleman that was blackmail-able enough.
In any case, precaution measures were to be taken in case of invasion - such as putting the rail car with gold in the Gotthard or Lötschberg tunnel just before blowing it up, or throwing it into one of the deeper lakes. It is of course possible to recover it from a depth of several hundred meters, but it wouldn´t be easy.
Switzerland was not just a neutral and a middleman - it was the only middleman that was blackmail-able enough.
In any case, precaution measures were to be taken in case of invasion - such as putting the rail car with gold in the Gotthard or Lötschberg tunnel just before blowing it up, or throwing it into one of the deeper lakes. It is of course possible to recover it from a depth of several hundred meters, but it wouldn´t be easy.