If you are choosing a safety school from the rankings, go for those between 30-40. I don't know about USC, but A&M is quite competitive, anyways both are very highly ranked.
You need to know why you're going back, if your plans have anything to do with academia then doing it part time will become unsustainable and you'll find yourself truly torn between the two. But if you just need your masters to move up in the company, then most ppl would just go for an MBA. I was in situation for almost a year before deciding to quit work to focus on grad school.
If you're interested in the faculty of more than one department and can explain it in your SOP, then i think its fine....but some schools only allow the application to only one department
Most useful: Engineering
Least useful: Everything else
Such a question is pointless really, because it will diverge into what makes a society successful...which is a too complex question to have any appeasing answer...
generally most recommenders send the same letter to all schools, but if you get the chance to do it yourself, be careful and try to make complete your SOP without repeating the same stuff, the LoR should portray from a different angle..