Well, then that's not negotiating, that's just words of support (not that there's anything wrong with that). Scotland has to have a referendum to get out of UK, and they have to get Westminster's permission for that for one thing.
I don't think so, not anymore. The SNP have a huge mandate. They have 56/59 MP's in Westminster, they also got elected in to the Scottish Parliament, again, and now we have Scotland showing in the EU referendum that the entire nation strongly wanted Scotland to stay within the EU.
The Tory party that called the referendum has no mandate in Scotland, yet the referendum affects us anyway. Scotland voted to remain but gets taken out anyway against it's will, which represents a "significant and material change" to Scotland's place in the union.
Sorry to disappoint but the SNP have the clearest mandate they could have to begin eschewing the hostage status we have in the UK and go out to forge our own path and actually make decisions that the people of Scotland agree with.
Everything has changed. The UK is at absolute breaking point. The EU referendum changed it all, and the results from Scotland give it every right to want to look after it's own interests now, whether the rules say they can or not.
EDIT: I meant to say that "Significant and material change" was in the SNP manifesto as the trigger point for another independence referendum.