I really don't see how a split between Scotland and England would hurt Scottish business at all. In fact, it may open up new opportunities as Scotland could forge the closer relations with the EU that England has long resisted.
A split between Scotland and England would bring down English income tax by 8p in the pound (that's the astounding net cost of Scotland, including all oil receipts).
If it brings English tax down by that much, it would drive Scottish taxes up by (I guess) 24p in the pound to maintain the current level of public services.