Divorce in Scotland is very different and the calculator doesn't really bear any relation to the capital settlement here. Scot's law aims for
Clean Break settlements and the financial independence from one another. Deferred payments and ongoing spousal 'aliment' are rarely awarded.
As far as
child maintenance is concerned the CSA will have jurisdiction for the 15 year old and the current rate is 15% of your net income for one child, minus deductions for any overnights you have the children. There is a calculator on the CSA website at;-
www.csa.gov.uk
The eldest will come under the jurisdiction of the courts and entitled in his own right to 'aliment.' Under the Family Law (Scotland) Act 1985 parents are liable for maintaining their children under the age of 25 years who are "reasonably and appropriately undergoing instruction at an educational establishment, or training for employment or for a trade, profession or vocation;"
The middle child is likely to come under the courts jurisdiction too, although maintenance would be payable to your wife (assuming she is the main carer.) Courts base their calculations on the needs of one party and ability to pay of the other so it's not possible to give you a ball point figure, you just need to negotiate with your wife. If you get stuck consider
mediation.
Perhaps you could consider paying your wife 20% of your net income (minus overnight deductions) for the two at home and 5% to your eldest as a starting point. This is in line with CSA guidelines - 20% for 2 children or 25% for 3 or more. You will also probably need to pay some 'aliment' for your wife for a period of up to 3 years to allow her to readjust.