This is economic illiteracy of a high order. After separation Scotland would still use sterling. So it would have to borrow in £s to cover its massive budget deficit and promise lenders it would pay back in £s (or they won’t lend). But after an unspecified transition it would move to a Scottish currency. But all the borrowing done during the transition would have to be paid back in sterling. If the Scottish currency plummeted v sterling (likely given the size of the deficit, lack of credit track record etc) that could become an unmanageable burden given the likely poor exchange rate. Scotland would have to borrow billions in its own currency just to convert to sterling to pay back lenders. Devaluing the Scottish currency further. What a shambles that would be. He has no idea what he’s talking about.