Found this Full Fact article which is interesting.
Although it is a couple of years old, I don't see that the proportions would've changed that much. In addition to the points that STDIW has just made, the proportion of exports to the England compared to the EU is not "4 times" and although it caveats the figures as they are not easy to calculate, it suggests that less than half of the oil and gas is sold to England.
There are also anomalies thanks to the the burden of the overpopulated South East of England. Things like the fact that despite the fact that Scotland is usually self-sufficient in energy, the power generators in Scotland have to pay to put their energy into the National Grid, while generators in the South get paid instead because it's based on proximity to population centres. 
In any event, for me personally, independence is not simply about the economics (although important), it is about self-determination. It's about making our own choices - and yes, on occasion, our own mistakes. It means we can't blame Westminster for our woes.
Ironically, a true federal solution or full fiscal autonomy (just paying for certain supranational requirements like defence which unfortunately would include Trident) would probably have satisfied up me up until a few years ago. But now I'm not sure I would trust anything that was proposed - unless, like happened in Ireland (but without the bloodshed that happened there), it was a stepping stone to full independence.