Your concerns implicitly depend on productivity per worker remaining constant over time. As that is not true, it's not clear that the changing retiree to worker ratio is as big a problem as you claim.
One solution to that problem might be replacing payroll tax with another tax that is closely correlated with productivity rather than wages.
Employers are paying more per worker except on the lowest tier, it's just that the increases have all gone into paying greatly increased health insurance premiums.
For unskilled labor wages haven't gone up because the job market was flooded with ten million illegal aliens. That's just a question of supply and demand.