Again, true, but its not like the independence referendum is on a knife edge, 'no' has quite a substantial lead, and it's very likely that it will stay that way.
'Losing' Scotland wouldn't be a disaster for the country, it'd be a disaster for Scotland, but the rest of the Union could cope perfectly well without them - it would also help the Tories electorally. And let's be honest, there's no love lost between England and Scotland, so if they did leave it's not like Cameron would be punished come election time.
As for the EU, leaving wouldn't be a disaster, and as with my previous point, we're a pretty eurosceptic country, so Cameron wouldn't be punished if we did leave, because we'd only leave if the electorate voted that way.