Alex Salmond is a has-been and he will always remain bitter about his defeat in the referendum and always angle for an excuse to have another one. He won’t find it though. If we left the EU, they’d have to present an even weaker economic case for leaving than the one that lost them the previous referendum. Scottish independence is a dead issue for the next 20 years.
Polls suggest otherwise — it looks like the majority of Scots would now vote for an out vote in the event of a Brexit. You are right that they have no economic case, but this, like the Brexit referendum is about emotions, not economics - and these are not rational (or even at times correct)