Your focus on the need for ARFF and a commercial airport to land at really shows a scary thought process for a pilot. Since you seem very interested in regs; you're saying that in this case it would have been better to go past the nearest suitable airport and not land as soon as possible (direct quotes from regs) after reaching the level of a fuel emergency, which for most 121 ops is 30 minutes of fuel remaining, than to try to continue on to try to land at an airport with Part 129 services. You're saying that landing at this airport was not safe? Would it have been safer to end up landing with 10 minutes of fuel remaining at a commercial airport? Hey, at least ARFF would be in the area when they come up 5 miles short of the runway and land on a highway!

Pop-up thunderstorms happen all the time this time of year and encompass entire regions of the US. It is not practical to carry enough gas to make the alternate completely outside of a weather pattern. Even with dispatch and ATC watching and communicating well, a dynamic weather pattern can catch up with even a GREAT pilot. Although it seems like these pilots made all the right choices along the way to add a non-required alternate, and have it updated as the weather changed, the weather did not allow for a safe landing, so the plan changed again!

I have been in 121 safety departments for awhile, having had the opportunity to see many different situations where decisions were made using emergency authority, and from the information available here, I'm confident that this crew acted in the best practices that I'd like to see if my family were on the plane.

Gojo: I would encourage you to go do some reading:
Avianca 52
Hapag-Lloyd 3378
ALM 980
United 173
TAM 3084

All commercial flights that crashed due to fuel exhaustion when viable options presented.

One of the most dangerous condition in flight is a pilot who won't make the tough decision, in this case to get on the ground safely when the opportunity presents, because they are so paranoid about having to explain their use of emergency authority!