//...and it follows that it might be argued that English ways are a drag on Scottish potential.//
Why? In what way do "English ways" (whatever they might be) drag down Scottish potential?
//45% of voters voted for independence, the SNP should get around about 40-45% of vote in the election//
It's not quite that simple. In 2017 (just looking at Scotland alone) the SNP polled 36.9% of the votes but were returned in 60% of the Scottish seats. So only about a third of those who voted in Scotland seemed to support the SNP. This is hardly the overwhelming majority they claim supports their (seemingly one and only) cause. Surely if the electorate in Scotland was champing at the bit for independence, more than a third of them would have voted for the only party committed to ensuring it.
Independence will be a far bigger deal for Scotland than Brexit will ever be for the UK (provided the "rump" of the UK that remains does not shower Scotland with money and gifts on its departure). Scotland has no currency, insufficient funds to enjoy the lifestyle it has become accustomed to, no realistic means of making up the difference and is currently responsible for 50% of the UK's annual deficit. None of these things apply to the UK/EU relationship.