Hi Umberto,
Thanks for the feedback. I did run the Live Update again with antivirus turned off and I was still getting the Couatl errors as shown by Berzerker above, both at FSDT airports (PHTO, KIAH) and default (KVPS). When at PHTO, I was not only getting Couatl errors, but my UTLive2 installation was repeatedly trying to initialize too and couldn't (not sure if there's a conflict).
Then I noticed that the GSX menu in the P3D's Add-On menu had only one option, Enable, although I don't remember disabling it previously. After enabling GSX, Couatl stopped crashing and the GSX and FSDT airports are fully functional.
Not sure what happened here. I started getting the Couatl errors after installing Flight Sim Jewels' Hawaii Plus photoreal package, disabling the necessary files for it to play well with Orbx's Cityscape Honolulu and FSDT PHNL (which I had installed previously), and installing the FSDT Hawaiian airports on top of that. Because these packages had to be set in specific order in the Scenery Library and they use different installation methods (FSJ as Addon Scenery, Orbx and FSDT via addon.xml), I had to use Lorby-SI's Addon Organizer to change the order. It showed my FSDT scenery entries as duplicated, so I used the option to remove duplicates, but I'm not sure if that contributed to the issue. I looked at add-ons.cfg, dll.xml, exe.xml and couldn't see anything wrong with them.
Regardless, I'm happy to have my sim and my add-ons back.