Re retirements - you have it back to front. My figures are based on past upgrades. If retirement changes in the near future from 55 to 60 you can add 5 years to my estimates. Since we have have a higher demand for captains and nowhere near enough training capacity, my guess is that 55 will go sooner rather than later.
That makes time to command 16-19 years, regardless of whether you join as an S/O or freighter F/O.