1) Without knowing your ENTIRE situation, business goals and retirement goals, unfortunately nobody can give you a good answer to that.
2) Salary is not based on a percentage of income, it is based comparable pay for the work performed. If he is the only worker and if it is a service-based business, it is likely that a very high percentage of the profit would be for the 'work' that he performs for the business.
This is really something that needs to be discussed with a GOOD tax professional that can analyze your ENTIRE situation and discuss the many potential cons of the S-election.