1. Not sure about the 55 y/o thing but, with your military retirement and the fact you'll be earning well into the 6 figure by the time you turn 55, you'll do fine.
2. Commuting... SUCKS. From Corpus, you'll have to get to IAH or DFW, then pay for a ticket to get to your freighter hub (LAX, SFO or JFK). It will be a year until hired so that can help pass the time the wife is in school. Then consider moving to the freighter base until your three years are up. To really make stupid money at CX you need to move the family to HK which is often a problem with working spouses (mine is). They often cannot get work permits in HK.
3. The app... fill it out best you can in Word and e-mail it. Then finish filling it out and fax it to HK, then UPS the whole package. I took three weeks total from the time my package was received until the call came for my phase 1 (later this week).
PM me if you want some other insights.
SG
VT-2 1988.