The NATO thing is REALLY simple. As a newly independent country, Scotland would not automatically qualify for membership. Instead, it would have to apply. Such an application would be unlikely to be rubber-stamped straightaway. Instead, Scotland would be invited to participate in the Membership Action Plan to prepare for possible membership, demonstrating in the process that it is in a position to undertake the commitments and obligations of membership, and contribute to security in the Euro-Atlantic area.
Albania and Croatia were invited to join NATO at the Bucharest Summit in April 2008 and formally became members when the accession process was completed on 1 April 2009. Currently there are four partner countries that aspire for NATO membership: Bosnia and Herzegovina, Georgia, the former Yugoslav Republic of Macedonia and Montenegro. Although it would take a few years, an independent Scotland would have little difficulty in joining NATO.