SeantheBrave. Official figures as contained in the most recent GERS report show total government expenditure in Scotland exceeding revenues from Scotland by around £9 billion, wihch number includes a demographic share of oil revenue (c£1 billion). An independent Scotland would however be entitled to its geographic share which is currently estimated at £11.7 billion, although that does fluctuate quite a bit year to year. That leaves Scotland with a nett surplus of about £1.7 billion per annum.
On the subject of defence spending, Scotland contributes about £2.9 billion of the UK's spend of £34 billion. Without the massive expense of SSNs and SSBN's, Type 45s, etc, i.e. with a defence forced scale down to our own needs and not those of a post-colonial would-be world peacekeeper, I suggest that £2.9 billion a year would buy a reasonable capability along the lines of Denmark, which spends just about the same amount.