Scotland has been a net contributor to the UK for most of the last 40 years.
Why on earth would Scotland be any less "viable" than Denmark, Belgium, Ireland... and other similarl sized countries?
Scotland currently has a large deficit and no oil fund... as a result of being in the UK. The way to improve the situation is to govern ourselves and make better choices than those made on our behalf. We won't solve problems created under the union by remaining in the union.
Whether Scotland leaves or remains in the UK it needs to make its own way in the world. Unionists seem to live In fantasy world where England is going to send free money to Scotland when the oil runs out. Fact is that the UK has net benefitted from Scotland for decades. They will not be eager to begin subsidising Scotland as the oil runs down.
Scotland needs to develop its economy no matter what. Staying in the union and asking for handouts is not an economic plan.
Scotland has huge resources ans potential and could be a very successful small country.