"1)Is it worthwhile to buy extra years service in the TRS system? Most calculations I've done show it's not the best use of money."
Here are the assumptions: Buy five years at a cost of $64k (calc. from last year). The pension without buying years or working in Texas is $30k. That is a pension based on 23 years. Because of adding one year of working at a much higher salary than existed in 2018 that increases the high five avg. salary, the new pension amount is a minimum of $40k. If I get a high paying teaching job, the pension goes up from there. How long does it take to recoup 64k? With those numbers it takes only 6.4 years, not including potential gains. (10k of gains x 6.4 = 64k) However, I don't plan to be super aggressive with my retirement funds in my 60s, so I am not including the gains in my calculation. Am I going to live longer than 6.4 years after I start drawing the pension? This plan has me starting the pension at age 61. My family tree indicates I should live to at least mid 70s, so that is a no-brainer.
If you say you're talking apples to oranges, because of the difference in the high five salary I suppose we could take out the increased salary to simulate making the purchase of credit neutral wrt the high-five salary.
If you were to do that, then the 28 years of pension is worth $36,717.66 per year. That is not considering the 29th year, which is the year I work when I come back to Texas. However, a person is not allowed to purchase service credit unless the person is currently working for the state, so it is hard to justify making that calculation, imo.